Another consideration would be to use fisher price motors along with the Cims. AndyMark sells a good gearbox that takes a fisher price motor and has the same output as a Cim motor (so you can mount it right into the tough box).
http://andymark.biz/am-0347.html
Although the fisher price motors are currently out of stock, you could order the gearbox by itself, or wait a few days for the fisher prices to come in (I called AM yesterday and they estimate having the FPs in by Friday).
Your concerns about shipping are valid, but my team has had good success with AM shipping, so I would say with fast shipping that would be a safe bet.
However, as other people have said, lowering your ratio is probably the best solution, unless there is some other issue associated with that.