A 32 tooth gear should put you where you want to be at (but possibly a 31 or 33 might be needed).
The metal screw on cable adapter is actually made out of a pot-metal material and is not quite aluminum (I believe).
I think it would be better to use the term screw on cable (metal adapter) vs. clip on cable (plastic adapter).
Aspen500 is correct, the gears for the metal screw-on cable adapters are much more plentiful than the plastic clip on gears are and are even being reproduced.
The plastic adapter/clip on style – it will be hard to find in a 32.
I have a box of speedometer gears of both styles, but not a single 32 tooth gear in the whole lot.
BudW