I put a few rounds through my son's P210 today, and it certainly is a fine shooting gun. He tells me that the original P210 mags are pretty pricey, and that he has done a bit of filing to make P210 Legend mags work with his Swiss P210 for that reason.

I think I'd start by talking to Sig if it were me. Some parts from the Legend may be compatible and some not; I hope you'll update us on this project as you get further along.

Well, assuming the Danish 210 uses the same parts as a SIG 210 (a big assumption, and one that I am unsure is even true), then Numrich Arms seems to have the slide stop in stock (part #41 at the link below), but make sure you are sitting down when you see the price.

Numrich Gun Parts Corp. - The World's Largest Supplier of Firearms Parts and Accessories

They are out of the recoil spring assemblies (part #13), and I cannot believe that is the case, based on the price they last charged for them. Wow.
I don't even want to talk about the magazines. This, from a guy who once paid $100 for a hi-cap pistol mag during the Assault Weapons Ban, too.
Allow me to suggest that you sell the parts of your pistol individually, and buy something really nice for yourself when you get done.

Good luck with your rebuild. Please accept my thanks for the education you arranged for me to receive while researching this info.
I had absolutely no idea .... none whatsoever...
Just ... wow.

Thanks for your replies guys.

I have a line on the parts that I need and made the recoil spring guide this afternoon. My gun will use a 45 ACP recoil spring as I am a shooter more than a collector. Didn't have to modify any SIG parts to accomplish my conversion.

Updates will follow when I can.