Best place to buy speedo gears?

[Tradered]

1990 PR w150, idometer and trip work, speed needle does not. Small gears should be 20 an 16 tooth. ??? Where is best/cheapest place to buy? Anyone have good part numbers? Thanks

 

[Weasle Min]

i tired junkyards for mine but had no luck and ended putting one from a chevy in but it has an extra tooth, it works but my speedometer shows about 3 under what im doing