I've heard it is costly regarding a wetsuit. Don't know about a semi-dry. I used to use a pretty must home made "external catheter". Got too complicated and worked only 60% of the time. So, I just stick the tubing in my bathing suit, down the leg and out. Flushes pee very fast. Of course it's not going through the hose, just along side it. After dives are over I have a 2 liter bottle of water to pour on my left leg, ETC. Not the greatest, but I have a life-long serious bladder problem not curable by any "drink/don't drink/eat this or that". I pee all the time. This is the easiest way for me. Just a thought, as it also just costs a piece of hose--which must be exactly the right strength/flexibility or it won't work. Good luck with the real pee valve.
Oh, I just discovered this today: I always leave my socks on while donning the wetsuit pants (farmer john). If you stick the end of the pee hose in the sock you don't have to struggle getting the hose down your leg. Then remove sock of course. Another today discovery: In 40F water your "pee" leg that flushes more doesn't get noticably colder than the other one. Of course at 40F you're pretty cold all over anyway.