Others mentioned sweetmarias.com which is great. I typically buy directly from a couple distributors at greencoffeebuyingclub.com. You can also check local roasteries in your area- sometimes they sell greens too (like Third Coast here in Austin).

Coffee roasting is a really fun hobby that has a surprising amount lore and detail. I highly recommend hanging around: https://www.home-barista.com/home-roasting/

^^ That forum has some really knowledgeable folks and lots of cool DIY projects to read about. Have fun!