I once was cuckoo for jelly rolls. This was my favorite online site to buy them:
https://www.jellyrollfabric.net/
because they are cut accurate, they are quality fabric, and they are decently priced.
Note: they are 20 strip rolls. And they are on sale right now. This site also has LOTS of free patterns to use with your jelly rolls.
Love free stuff.
BTW...I am not affiliated with this website in any way, just liked their rolls. I don't buy them much anymore because I still have lots to use up first.