That's the wonderful P9 trigger. If it's not a surplus pistol and in decent shape....great price. I've never had an issue with any 9mm ammo in my pistols. I only have factory mags for my stuff, so no idea about the cheaper replacements.
You might try Adam at HKParts.net. You have probably already realized that Numrich doesn't have them......other than that, you haunt GB and Ebay hoping for a set of grips that come with the screws to pop up. You could try H&K USA. You never know. What's wrong with the ones holding your Pachmayr's on?Where can I find grip screws?