Well it is not nearly complete, but I found something.
First of all a list of major companies accepting bitcoin according to a recent article on Yahoo Finance. These are not necessarily the companies that handle most bitcoins, simply the largest ones that accept it for some purchases.
- Microsoft: Accepts it for digital content, did not find numbers
- PayPal: I don't consider paypal a 'shop', but if numbers are known I guess it would count as an enabler.
- Overstock: Reported about 3.6M annual bitcoin spend by its customers in 2014 (and expressing the ambition to see that grow fast)
- Wallmart: Did not find a report, but it seems they go via a provider (perhaps cashapp), see below.
- Whole foods: Did not find a report, it seems they went through Square, which now holds CashApp.
- Etsy: Does not currently appear to accept Bitcoin payments, but encourages users of the platform to do so manually
- Starbucks: The news was a bit fuzzy, but it seems Starbucks declared they do not actually accept Bitcoins yet. It does appear possible to use bakkt to charge a Starbucks card. But I am not sure if I would consider card balances 'shop payments' as cards are purely financial items.
- Newegg: This seems like a site that actually accepts BTC directly, they mention there is a 15 minute delay and no regular refunds, suggesting there is no intermediate party doing a dollar transaction. Did not find out which fraction of their 2bn revenue comes from BTC, but they are using Bitpay.
- Home Depot: Did not find any earnings reported, presumably because the conversion to USD occurs before Home Depot finishes the transaction.
- Rakuten: These guys seem serious, as they even created the Rakuten wallet. However did not find revenue for this wallet, or an indication of whether it is used mostly for shop payments or financial purposes. Perhaps there is more info available for those fluent in Japanese.
- Twitch: Had to click 'more payment options' twice before bitpay showed up, but perhaps it is more prominently featured to other regions or users. As such it may not be large, but on the other hand the nature of the business (anonymous donations, and almost pure focus on revenue rather than margin) may lend it well for coin payments.
Another way to look at the question is by companies that enable transactions to shops. Paypal could be one.
- CashApp: It is hard to estimate which fraction of this is actually going to shops, but they reported a revenue of over 1BN, and others mentioned this could be a few BN by now but it seems this is becoming more weighted towards financial services 'typical shop' payments.
- Bitpay: In 2018 they reported a revenue of about 1BN
This is quite a wild estimate, but as the definition of 'shop payments' loose anyway:
Based on the above, I would guess the global annual shop payments with Bitcoin is somewhere between 10 Million and 1 Billion USD. I know it is a wide range, but at least it is something, and refinements or additions are welcome.