Get the model number from it and what configuration the jack(s) might be. Wiring up a footswitch might not be too hard, especially if it's separate 1/4" jacks. If it's a single DIN plug it might be a bit trickier, but schematics might be available.
If it's separate 1/4" jacks, a standard 3 button footswitch for a guitar amp would be usable, they can be found at guitar oriented shops and sometimes pawn shops. many nusic stores have a lot of them from amps they sold and customers didn't want or didn't know a footwswitch was included. I got all of mine from pawn shops and rewired them to suit the amps, and one I made form the case of an old Ross phase shifter that was shocking the original owner so he scrapped it and gave it to me. Now I wish I still had the guts, I might be able to get it working again.
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