I can't afford either, but only feel like a real man if I can use the urinal.  Anyone have any tips? 

You could try and see if any guys have an STP they bought but don´t like. Some guys sell their stp cheap. If you really want to use the urinal, I´m not sure there are any other options.

If it´s just standing to pee, you could use the regular toilet and make your own stp cheap. It´s quite easy.

you should check out the FTMgarage, its a live journal blog that folks use to sell they're ftm gear that can not be returned or sold on more public spaces like facebook. I've bought and sold tons of stuff the last few months on there. Most people just get an STP that doesn't fit right, look right or work right for them personally and try and pass it along. Very nice space to score a cheaper FTM product.

ummmm ... i'd really rather not use a used stp.  Are there easy ways to modify pants or something? 

Just to put it out there: a vast majority of STPs can be 100% sterilized if bought secondhand. It's likely the seller would do that for you anyway before sending it off.

Just my experience, I have not found a STP that I have confidence in it not leaking to use it at an urinal. I have seen a few places where the urinal were in a stall like setup with no door.  I just haven't been able to make a STP work dependably enough through the fly in my pant.  This has been experiences; I do keep trying at home and hope to a way that would work at an urinal in a public restroom.