Anything from 120 or heavier should do it. I play in Drop-Db with 110's at nothing faster than 180 and those flap around a bit but it's part of my tone somewhat.
If you've got strong enough hands, you could get a lighter gauge 5-string set and simply tune the B up a tone. That would be very tight.
Another thought: depending on how heavy you go, you might have to drill the string hole in the bridge slightly if it's built for standard 4-string gauges (not the best idea on someone else's bass

). The groove on the bridge saddle should be fine though. I had to do that on an old bass I used to string B-E-A-D.