I can't tell you the name but it looks like the spring guide assembly the old Gamo Shadow used. If true, many years ago I wanted to put an aftermarket spring in a Shadow but the spring had a larger ID than the guide and I wanted it to fit tighly. I ended up cutting off the guide portion and used a custom guide assembly like the R9 uses -- worked great.
I doubt if Gamo would sell just that part but you might find a used one that's been abused in a pawn shop for cheap that you could use for parts.