Square butt N frame target grips from Thailand (well under $100 new and shipped, available through eBay) or try to locate a set of used SW stocks. You might find a set for right around your price. They'll be a little worn, but for a shooter, who cares? You can alway put the originals back on for display purposes. Check the classifieds here. Those grips come up for sale fairly frequently.
Are the ones from Thailand decent quality? I have a set on my watch list now.