I recently bought a set of Pachmayr and Hogue grips from Midway's UK website. I probably paid more than I would have done direct from the US but there were no hassles. I tried both and kept the Hogue as it suited my small hands better. The Pachmayr sold here in seven minutes....

There used to be an official shoulder stock for the HW45 so I suspect the holes in yours are to take that.

Jonathan