Do you want a cassette combination Shimano doesn't make? We carry many individual sprockets for Shimano cassettes, and can provide most sizes. The most economical approach to custom cassettes is to buy a stock cassette that has most of the gears you want, then an additional sprocket or two to substitute for the un-wanted sizes. Although the Hyperglide ramps don't necessarily line up with non-standard sprockets, as a practical matter they tend to work just fine, even if they make a little click when you shift.
Note, in most cases, the smallest sprocket must have a built-in spacer, so, for instance, if you are converting 12-27 into a 13-32, you'll need to buy a new 13, even though the 12-27 comes with a 13.
The differences in thickness between 7-, 8- & 9-speed sprockets that don't have built-in spacers are so small that substituting 2 or 3 in a cassette won't have any affect on the indexing. Similarly, 8-speed top-position cogs work OK with 9-speed cassettes, even though the spacing is different, because the indexing for the smallest sprocket is regulated by the high-gear limit stop of the derailer, not by indexing of the shifter as with the other gears.
Individual Hyperglide Cassette Sprockets
Flat sprockets $9.95 each. 
Sprockets with built-in spacer (generally the smallest sizes, for top-gear use). $19.95 each.
For single speed applications, we also carry the BMX Freehub sprockets, which fit all Shimano Freehubs. See our Singlespeed Page.
