You'll probably have to contact Smith and Wesson. They took over all of the Walther business from Interarms a few years ago. However, the TPH hasn't been made for a while, so hopefully they have Interarms supply of parts.
S&W said call Earl's.
Earl's only works on German guns and calls the US ones "pieces of crap". They say S&W should take care of them since they took over Walther USA.
Basicly if you need something for a US gun you are screwed
I found one place that has some parts and have a part list on the way, we will see what they have.
I will probably get a few spare parts just to have them.
Also found a place to make a new barrel if needed, so with a little tinkering it should be great
Still came out ahead on price and when it works like it ahould it will be worth it