I buy Qualatex from Amazon, 250 for about $18 shipped. I heard they were good and is what I use. I don't use them often, but I bring them out when we having parties and make swords and hats for the kids.

These are what I ordered, I'm almost out of the first pack but think I've had maybe 2 failures.
https://www.amazon.com/gp/product/B001DAYNYK/ref=oh_aui_search_detailpage?ie=UTF8&psc=1