PT ? yes, big investment 
[ since you are here, I suppose you already have a Pimax4K ]
- used PSMove controler & PS3Camera => 10$ [ but PSMove is needed only for first configuration / if you could borrow for a day then only camera = 5$ ]
- driver with full licence - to have all further upgrades without time limit => 8E [ but works in demo mode up to 10 minutes = 0$ ]
- a little PLA plastic for my 3Dprinter => couple of cents [ but a pingpong ball will be more then enough ]
- a 12VLED => 1-2$
- time