There's nothing wrong with having more frames and the best way to get em is to just buy another rifle!!! I'm at 16 frames now and there's still room for more!!! If you just want a frame there was a late model SB2 frame in the classifieds for less than $100 shipped. If you can, get one made '99 of later, H&R increased the frame strength then and it can be used with any centerfire caliber they make.
Tim