Figure of 8 or dot the i, if you've got the dough, give 'em a try - AmeriGlo i-Dot Night Sight Set for Walther PDP

I started looking for something like this when I realized I liked the sights on my PPK better than the 3-dot sights that came on my PDP. I don't currently use a red-dot type optic or anything like that; and the 3-dot default PDP sights were a bit distracting in my vision.

I pick up these sights really well peripherally, and the figure of 8 alignment is a bit easier for me to align while keeping my eyes down range.

I'm not a tinkerer, so I'm unlikely to change these out. I bought the sight pusher tool from Walther to swap these out and make my own adjustments when zeroing. They're pretty tight to install.