Prime Now pickup slot finder (UserScript to be used with https://www.tampermonkey.net/ in Chrome)

primeNowPickupFinder.js

// ==UserScript==
// @name         Prime Now pickup slot finder
// @namespace    AZ
// @version      1.0
// @description  Find available slots for Whole Foods order pickup
// @author       Andrei Zharov
// @match        https://primenow.amazon.com/checkout/enter-checkout*
// @grant        GM_notification
// ==/UserScript==

// settings
const delay = 30; // In seconds
const alertAudioUrl = "https://soundbible.com/grab.php?id=2154&type=mp3";
const alertDurationSec = 5;

(async() => {
    console.log("Whole Foods pickup: ", new Date());

    let noPickupAvailable = false;
    try {
        noPickupAvailable = document.getElementById("delivery-slot-form").innerText === "No pickup times available";
    } catch (err) {
        console.error(err);
    }

    if (noPickupAvailable) {
        console.log(`No pickup/delivery, refreshing in ${delay} seconds.`);
        setTimeout(() => {
            console.log("Refreshing");
            window.location.reload();
        }, delay * 1000);
    } else {
        GM_notification({
            text: "Pickup slots available. Order now",
            title: "Prime Now pickup slot finder",
            timeout: 5000,
            onclick() { window.focus(); }
        });
        console.log("Pickup/delivery slots found, playing alert");

        const alertSound = document.createElement("audio");
        alertSound.src = alertAudioUrl;
        alertSound.preload = "auto";
        alertSound.loop = true;
        alertSound.play();

        alert("Found slot. Order now!");

        setTimeout(() => { alertSound.loop = false; }, alertDurationSec * 1000);
    }
})();

Add items to your cart and then go to checkout page