BBB cassettes have individual sprockets and spacers, but I donīt know if their individual thickness matches Shimano sprockets & spacers.
http://bbbcycling.com/bike-parts/cassettes/BCS-10S
Maybe ask them on Facebook:
http://www.facebook.com/BBBcycling
Shoot Chris at Highpath Engineering an email if you havenīt already. He will know what the options are and his shipping worldwide is only 4 pounds. I really recommend you contact him - when I was trying to attempt something similar he was really helpful.