The Ruger factory hi caps are around, but they aren't cheap. On some web sites, I've seen them as high as $70. I have five hi caps total, and I payed between 50 and 60 apiece at gun shows for three of them (new). But you can run across a deal now and then. I just got two new ones for $32 each the other day on eBay--only because the seller didn't advertise them as hi-caps. If he had, eBay administration would have yanked the auction.
Still, even with this good deal, I'm averaging $48 a mag, so you're likely going to spend some money if you go after the factory mags. Many people on the Ruger forum swear by the factory mags best, but Mec-Gar is supposed to work well in the P series. Last gun show I went to though, a lady wanted $50 for her Mec-Gar hi-caps. Might as well get the factory mags at that price.
Good luck. As one poster noted, the Ruger factory hi-caps often seem to be made out of unobtainium these days.
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Guyon
NRA & GOA Member
Vote for your rights!!!