As stated above, the receiver is grooved for rimfire rings. If you have a set of those, you're fine.
If you need to buy rings, I think that I have a base for a 597 kicking around in one of my spare parts/junk drawers, which will allow you to choose from a big selection of Weaver-type rings. It's yours gratis if you want it. You'd need to scrounge some screws, but any gunshop has them. PM me.