I'm wanting to build a Supergun for as cheap as possible... I'll improve on it later if I think it needs it

So... my plans so far:
PC power supply
JAMMA harness (of course)
Controllers - I already have some I can wire up for the purpose
The only thing I'm unsure of is the TV output... I'm stuck with composite because I'm not going to buy a new TV

(not YET anyway...)
I've heard you can use
some console to TV adaptors, but which ones? Can anyone recommend one that will work?