G20 Gen4 slide manufacturers

[Labrat198]

Looking for a second slide to put on my G40 but all I can find are Gen 3 slides in 10mm.

I love my G40 with Deltapoint Pro for days at the range and for hunting, however the reddot just collects wood chips and grass clippings when I am working in the woods. My understanding is that the Gen4 G20 uses the same frame so it should be a simple swap. I have found a few stock uppers for sale on auction sites from time to time, but was interested in something a little more customized.