Originally Posted by james_swift
Could you give us a close-up of your stem/gripshift-mount mod?
Is a description sufficient? Instead of the original handlebar I mounted a piece of a cheapo seatpost that fortunately matched both diameters (the gripshift clamp diameter and the somewhat larger stem clamp diameter). The cheapo seatpost is one of those old versions, where the seat/rail attachment clamps onto a pipe. Sometimes those can still be found at department store bikes. That's where mine actually came from.
I guess cutting down the handlebar would work as well, but I much rather salvaged that old seat post than the new handlebar.