Large Reduction Single Speed Gearbox

[ASD20]

Are there any single speed COTS gearboxes with a reduction of around 22:1-25:1? So far the largest reduction I've seen is the WCP SS Gearbox, which can be configured to about 19.28:1. I know that there are some 2 speed gearboxes with that large of a reduction, but I would prefer not to spend twice as much money for a shifter with an unusable top speed.

My team is planning on using 8 inch wheels so the large reduction is necessary to get to a goal speed of roughly 7 fps.