I would check out The Assault Group miniatures. They have an equipment section which includes separate weapons from some of the major nations. I got some SG44s and Panzerfausts from them a few years ago, decent amount of detail too.
You might want to try The Assault Group miniatures. The parts and equipment section has Panzerschreks and Panzerfausts available separately, so no need to drop $40 on a 40k kit. I’ve used some of their parts before, added STG44s to some plastics. Detail and Casting quality are decent too.