Recently bought a monocog and I would like to mount a fixed cog to the unused 6 bolt iso disk mount on the rear wheel for a fixed gear option. Boone makes an amazing Ti cog that does exactly this but the time to machine and cost are prohibitive. The instructions on www.63xc.com cite using a shimano DX cog. That and every other cassette cog or driver cog I can find are 3/32". So, where can I find a 1/8" cog suitable for drilling?