Whatever you do, don't get a newer TV rotor--make sure it is a good quality older unit. Most of the newer ones have plastic gearing that will strip out if too much of a load is put on them. If the rotor is a good one that would turn a long log-periodic TV antenna, it may do OK for the MA5B.
Yeah I should probably have stressed that my rotor is an older one. It's called a Gemini OR-360 and it has metal gearing. It also has a position pot. I've got a homebrew rotor box controlling it and can steer it by PC using a program that interfaces with various logging software. Unfortunately they don't make these rotors anymore and they are hard to find used.