Dovetails on target rifles despite looking and supposedly measuring the same will differ enough for things not to fit. If you look at a shop like Intershoot you'll see that when you select a fore or rearsight it will ask you the make of rifle to ensure they send you the version which will fit.

So you'll want something that's been made for a walther, either walther own brand or a sight or set of sights made to fit one. Most big makes like Centra and indeed Anschutz have versions to fit.