Why do you think that is a 3 phase motor? It looks like a garden variety six wire single phase motor to me.
I bet there is a capacitor there somewhere.
At any rate you need a double pole double throw switch. They do make them that sit in a plastic bubble that replaces the wiring cover. If you can come up with a way to mount a "4 way" switch like a handy box connected to the threaded hub where the power comes in with a close nipple and feed the power cord through, you would extend the red and black into the box and hook them to one side of the switch, Bring out the other side to the terminal block. What they call a "4 way" is simply a reversing switch, typically used for "3 way" lighting circuits. Just be sure you buy one that will handle a motor load. (20a spec grade should do it)
Something like this
https://www.homedepot.com/p/Leviton...UgzoEAQYBCABEgLlufD_BwE&gclsrc=aw.ds 
