Where can I buy Sig X5 aluminum floor plates for mags?

Nothing in the Sig Store. I would call them and ask since they are coming out with american made 226 x-5's.

Check Mec-Gar and Armory Craft.

If you are talking about the silver Plus 2 base plates, I have been on the same hunt lately. You can find the German Mastershop originals from Vanguard or very close replicas from Mec-Gar for $66 but out of stock OR a reasonable repop from Armory Craft for $30 to put on your own magazines.

Not in stock at the moment, but Greg has had the mec-gar ones on a regular basis. That's what I have been using.

Thanks for info guys.