Mixing containers are something else I get from Amazon as well... last time I ordered some this is what I got:
www.amazon.com/.../ref=oh_details_o02_s00_i00
Look around though there are lots of options for small mixing containers on Amazon. Another option, if you really want glass, is to go over to Goodwill or even Walmart and get some cheap plain shotglasses... those are great for paint mixing if you don't mind the cleanup. For me, though, disposable is the way to go. A good palette, too, would be a glass ashtray - nice, wide, and flat but with raised lip... makes it pretty useful. Cigarette notches on them are great for holding brushes during use too.
For those who have not tried droppers and want to try a smaller pack, this is what I got - different manufacturer but these are what got me hooked on using droppers for all my paint needs.
www.amazon.com/.../ref=oh_details_o01_s00_i00