Any cheap synth like a MicroKorg or iPad setup would get it done. For bass guitar you'd probably want something like the Panda Midi Future Impact.
But really just play it on a regular bass, no one will notice or care.
There is no cheap way to do it on a bass guitar. The Future Impact is really the only pedal that could pull it off and its $400+. If you do a lot of dance tunes it might be worth being able to do it on keys. Not as fun to play keys though.