InventoryRetriever.java

package com.mozu.mozuandroidinstoreassistant.app.loaders;

import com.mozu.api.MozuApiContext;
import com.mozu.api.contracts.productadmin.LocationInventoryCollection;
import com.mozu.api.contracts.productruntime.Product;
import com.mozu.api.resources.commerce.catalog.admin.products.LocationInventoryResource;

import rx.Observable;
import rx.Subscriber;
import rx.android.schedulers.AndroidSchedulers;
import rx.schedulers.Schedulers;

public class InventoryRetriever {

    public Observable<LocationInventoryCollection> getInventoryData(final Product product, int tenantId, int siteId) {
        final LocationInventoryResource inventoryResource = new LocationInventoryResource(new MozuApiContext(tenantId, siteId));

        return Observable
                .create(new Observable.OnSubscribe<LocationInventoryCollection>() {
                        @Override
                        public void call(Subscriber<? super LocationInventoryCollection> subscriber) {
                            try {
                                subscriber.onNext(inventoryResource.getLocationInventories(product.getProductCode()));
                                subscriber.onCompleted();
                            } catch (Exception e) {
                                subscriber.onError(e);
                            }
                        }
                    })
                .observeOn(AndroidSchedulers.mainThread())
                .subscribeOn(Schedulers.io());

    }

}

ProductDetailInventoryFragment.java

package com.mozu.mozuandroidinstoreassistant.app.fragments;

import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;

import com.crashlytics.android.Crashlytics;
import com.mozu.api.contracts.productadmin.LocationInventory;
import com.mozu.api.contracts.productadmin.LocationInventoryCollection;
import com.mozu.api.contracts.productruntime.Product;
import com.mozu.mozuandroidinstoreassistant.app.R;
import com.mozu.mozuandroidinstoreassistant.app.adapters.ProdDetailLocationInventoryAdapter;
import com.mozu.mozuandroidinstoreassistant.app.loaders.InventoryRetriever;

import java.util.List;

import butterknife.ButterKnife;
import butterknife.InjectView;
import rx.Observer;
import rx.Subscription;
import rx.android.observables.AndroidObservable;

public class ProductDetailInventoryFragment extends Fragment implements Observer<LocationInventoryCollection> {

    private Product mProduct;

    private int mTenantId;
    private int mSiteId;

    private List<LocationInventory> mInventory;

    @InjectView(R.id.inventory_list) ListView mInventoryList;
    @InjectView(R.id.inventory_progress) ProgressBar mProgress;
    @InjectView(R.id.dialog_header) LinearLayout mDialogLayout;

    private Subscription mSubscription;

    public ProductDetailInventoryFragment() {
        // Required empty public constructor

        setRetainInstance(true);
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        mSubscription = AndroidObservable.bindFragment(this, new InventoryRetriever().getInventoryData(mProduct, mTenantId, mSiteId)).subscribe(this);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.product_detail_inventory_fragment, null);

        ButterKnife.inject(this, view);

        if (mInventory == null) {
            mProgress.setVisibility(View.VISIBLE);
            mInventoryList.setVisibility(View.GONE);
        } else {
            onCompleted();
        }

        return view;
    }

    @Override
    public void onDestroyView() {
        mSubscription.unsubscribe();

        super.onDestroyView();
    }

    public void onNext(LocationInventoryCollection inventoryCollection) {
        mInventory = inventoryCollection.getItems();
    }

    @Override
    public void onCompleted() {
        mProgress.setVisibility(View.GONE);
        mInventoryList.setVisibility(View.VISIBLE);

        mInventoryList.setAdapter(new ProdDetailLocationInventoryAdapter(getActivity(), mInventory,mTenantId,mSiteId));
    }

    public void onError(Throwable error) {

        Crashlytics.logException(error);
    }

    public void setProduct(Product product) {
        mProduct = product;
    }

    public void setTenantId(int tenantId) {
        mTenantId = tenantId;
    }

    public void setSiteId(int siteId) {
        mSiteId = siteId;
    }

}

Actually one more thing i just noticed.

You should change the line

Subscription mSubscription

to something like

Subscription mSubscription = Subscriptions.empty()

This should insulate you from any NPE errors if you decide to change where you subscribe and unsubscribe