Welcome to the Forum!
Belt Mtn makes some nice ones,, but if it's a Ruger,, and a New Model,, why not contact Ruger?
If it's an Old Model,, and you want an original,, place a WTB ad here in the classifieds.
Black Spot, Welcome to the forum. You never mentioned "why" you needed a new base pin! If it's simply to replace a "lost" one for a NM Ruger SA then order a "standard" one from Ruger or Brownell's. Some guns require "modification" (minor fitting) for a Belt Mountain base pin and you may not want to go this route. They are also a lot more expensive than the Ruger base pins...............................Dick :wink: