You really are asking alot. Halo Spin Doctor Disc Rear 10mm | Buy Online | ChainReactionCycles.com
This is another British Out Fit, but shipping to the USA is only $8.35. 48 Hole Disc Brake Cassette hubs are very limited in availability. These days in the US you only find them on High End Tandems, or custom Loaded Touring Bikes, both very small markets. Shimano has one $245.00 I'm sure you could find one from Phil Wood (cost? $400,00+) Peter White Cycles probably has one as well costing several Hundred dollars. Try Google and see what you come up with.