Have you tried Harris citrus? They have quite a selection. If it's not on their site, you can call and ask Ruth. She's really nice and sometimes has other stuff almost ready to go that has not been listed.

http://forums.gardenweb.com/discussions/4069219/list-of-us-citrus-suppliers?n=63

citrus trees

6b Steve

similar choices
sweet lemon variety

Palestine Sweet Lime

This is the season to buy millsweet lemons for eating and seeds

I did a bit more research and realized that what I am seeking is "Citrus limettioides Tanaka" a.k.a. Chaaksi (चाक्सी) in Nepalese. I am dreaming about drinking a tall glass in my NYC home while recalling Kathmandu. Here's a link about it: http://theindianvegan.blogspot.com/2013/03/all-about-sweet-lime-mosambi.html So far, I don't see that available at any of the sellers on the citrus list (including Harris). If anyone has any thoughts - or a seed they can send my way - I'd appreciate it! Thanks