UIWebView does not allow to customize the `inputAccessoryView` without using magic. Just simply change the `customInputAccessoryView` property to switch to another view. Inspiration from: https://gist.github.com/bjhomer/2048571

UIWebView+CustomAccessory.h

#import <UIKit/UIKit.h>

@interface UIWebView (CustomInputAccessoryView)

@property (strong, nonatomic) UIView *customInputAccessoryView;

@end

UIWebView+CustomAccessory.m

#import "UIWebView+CustomAccessory.h"
#import <objc/runtime.h>

@implementation UIWebView (CustomInputAccessoryView)

static const char * const kCustomInputAccessoryViewClassString = "UIWebBrowserViewCustomAccessoryView";
static Class kCustomInputAccessoryViewClass = Nil;

#pragma mark - Accessors

- (void)setCustomInputAccessoryView:(UIView *)customInputAccessoryView
{
    objc_setAssociatedObject([self browserView], @selector(browserViewCustomInputAccessoryView), customInputAccessoryView, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    [self loadCustomInputAccessoryView];
}

- (UIView *)customInputAccessoryView
{
    return objc_getAssociatedObject([self browserView], @selector(customInputAccessoryView));
}

#pragma mark - Browser View Custom Method

- (UIView *)browserViewCustomInputAccessoryView
{
    return objc_getAssociatedObject(self, @selector(browserViewCustomInputAccessoryView));
}

#pragma mark - Helpers

- (void)loadCustomInputAccessoryView
{
    UIView *browserView = [self browserView];
    
    // Register a new class if needed
    if (!kCustomInputAccessoryViewClass) {
        Class newClass = objc_allocateClassPair([browserView class], kCustomInputAccessoryViewClassString, 0);
        IMP newImplementation = [self methodForSelector:@selector(browserViewCustomInputAccessoryView)];
        class_addMethod(newClass, @selector(inputAccessoryView), newImplementation, "@@:");
        objc_registerClassPair(newClass);
        kCustomInputAccessoryViewClass = newClass;
    }
    
    // Switch to the new class if we haven't already
    if ([self class] != kCustomInputAccessoryViewClass) {
        object_setClass(browserView, kCustomInputAccessoryViewClass);
    }
    
    [browserView reloadInputViews];
}

- (UIView *)browserView
{
    UIScrollView *scrollView = self.scrollView;
    UIView *browserView = nil;
    for (UIView *subview in scrollView.subviews) {
        if ([NSStringFromClass([subview class]) hasPrefix:@"UIWebBrowserView"]) {
            browserView = subview;
            break;
        }
    }
    return browserView;
}

@end

Can I only edit the view, meaning to keep the previous/next add new buttons? I believe, there must be some NotificationCenter notification the next/previous buttons are conveying. Do you happen to know them?