I've seen a thread somwhere that even had pictures :11:
The wetsuit p-valve isn't as complicated as the drysuit p-valve- you could even make one for about $5 from the scuba aisle at the local hardware store. It's essentially a barbed fitting, a bit of tubing, and then a right angle barbed fitting to exit the suit. Don't worry, the barbed fittings aren't as painful as they sound.
I recently made a few modifications to my drysuit p-valve. The 3/8 OD barbed fittings seem to fit the catheter condoms well. I used the white nylon ones- the brass ones might give you a rash! You could reduce to smaller tubing, but I wouldn't recommend anything smaller than 1/4 ID, or else you would be peeing through a straw, figuratively speaking
I just used the clear plastic tubing in the plumbing section. Then to finish the whole thing off, use a right angle barb fitting to exit the suit somewhere in the crotch. Just be sure it won't poke you in unpokeable places. I suppose you could even glue this in place so that it would lie down and reduce the seepage. Be sure to leave the hose long- about 18"- this will make you feel better, make it easier to hook up, and will give you some slack so that you can move around.
This would be an unbalanced p-valve, but you wouldn't need to balance it in a wetsuit. You could add a check valve (in case you are afraid of candiru critters) but that is beyond my experience.
Good luck and if anything bad happens, I am not responsible!