I think if you find a guy (girl) who is decent at keyboards then he/she should be able to handle left hand bass. It really only requires a good knowledge of scales and intervals. Rock bass lines, for the most part, are pretty easy; pop too. Jazzy type songs require that walking bass and a person needs to know keys & scales.

If the person you get is no better than you, then why hire them if you could do their job. Again, footpedals are a good possibility.