Hi, @annyeryn29 !
Ryder here, from the Social Care Team at Shopify. Thanks for posting! There are a few apps that you can look into that may be able to support this. Most of them have free plans or free trials available, so you can test out whether they work for your business needs. Alternatively, you can reach out to the app developer for support.
My colleague personally uses Infinite Options and tested it out on his shop. He was able to get it working so that if you have four in stock, and customers checkout with four any selection of the available variants, the product would then be sold out.
This is how the cart appeared with four variants added:
In contrast to what appears if more than four variants are added to the cart:
I hope this helps answer your question! Because we offer limited third-party app support, it’s always best to check with the app developer for more information. If there is anything I can clarify on the Shopify side of things, please let me know.
Cheers.