What is sold in barbecue shops is often processed by them themselves.

Customers in supermarkets rarely buy meat, so the kind of finished meat you mentioned that is round after being cut is often not sold.

If you really want to buy it, you can go to some wholesale meat markets and check it out. There may be meat suppliers in some stores who will sell it to you.

However, it may be somewhat different from what you see in a barbecue restaurant.