fietsbob: Thanks, but I don't want to replace the wheel and freehub if I don't have to. I actually just found the cassette online at two different places and confirmed that one of them does have it in stock brand new for $30.
Hillrider: The $17 Shimano HG41 cassette you pointed out indeed does have an 11-tooth inner/top cog and is 7-speed just like my HG70-C cassette, but the listing says it is compatible with the Shimano Hyperglide, not the Hyperglide-C version which is the compact version of the hub and is the one I have. Correct me if I am wrong but I don't think it would work and so I should get the exact same HG70-C cassette.
Thanks for reminding me about the chain. I will get a new one. The crankset I have has the label Shimano biopace-SG and 'for NARROW chain only' on it so I'll have to get a narrow chain (whatever that means).
Last edited by BikeToronto; 02-04-12 at 12:23 PM.