footswitches/pedals

hey, whats the cheapest footswitch you can get for a 2500?

I really don't care what it's like as long as it will change the pad bank when I put my foot on it.

I don't even know how it all works....what do I need to look out for? how can a jack change something in the mpc ehhhhhhhhhhhhhhhhhhh?

thanks for any advice you can give.