speedo gear info request

[texasmark1]

...for a typical 57 3 spd, non-overdrive tranny...

mine has a few loose teeth so figuring on replacement...

12 teeth on the small end and 20 on the big end...

Concours wants $21.00 !!!

ebay for something that looks and specs similar for $5 BIN...

plus there are different colors out there...!!?? does this mean anything?

as long as the speedo works and is "fairly accurate"... that's all I want...

any suggestion/input on getting one??
thanks,Mark