I bought a 1.2 gallon toilet. I have to replace the flapper> home depot sells universal 3 inch flapper. When I tried to swap out ,original was a little different than eplacement. Toilet still leaking. Where can I buy glacier bay flapper?

Since GB is a Home Depot brand, they should have one. If not, explain your issue and they may give you one from a display model.

This link may help, How To Find Your Toilet Flapper - Find Toilet Flapper Good luck, Tom