From the Lomography website:
ohio
banyan tree
2242 prodessor ave
cleveland, oh 44113

columbus museum of art
480 east broad street
columbus, oh 43215
tel 614-221-6801

They are usually also available in Fine Art Museum bookstores, some university student stores, and Urban Outfitters.

For how to videos on Holga and Diana cameras, check out my youtube channel:
http://www.youtube.com/user/kaituba

I also have tips and tricks up on my website:
http://dianacamera.com/