I should think that any holster that pulls the grip in tight to your side would take care of any, 'patterning' problem you might have. I'll confess, however, that my everyday carry piece is a really large Glock Model G-21 that I like to carry IWB.
I, also, use a Walther PPK-S. I carry it with 2 extra magazines. To get around the problem you've described I put finger-groove extensions on all 3 Walther magazines. Anyway, by the second magazine something (or somebody) should already be bleeding - right!