A search for "Earl's Repair Service, Inc." brings up the Walther website for which they are dealers. It shows the P5 as an order item, though I can't say if it's actually available, even if you wanted to spend $1500+ for it.
I owned one for a short time in the late Eighties. It was okay, accurate and reliable and such, but the double action reach was a little long for my short fingers. The thing I really didn't care for on mine was the poor machining on the receiver above the trigger guard (much worse than the pics in this thread). It basically didn't do anything better than other things I already had, so it went to someone else with no regrets.