Well, since you did try web searches, I certainly can't berate you for giving it the good old college try. One company that made guns for the 45 Win Mag was Automag, whose Mark I pistol was the original gun to chamber the 44 Automag pistol. That was too expensive to produce, and Automag started moving around like a floating crap game from one owner to another, and IIRC, I think one of their Mark IV Series was chambered for the 45 Win Mag.
https://en.wikipedia.org/wiki/AutoMag_(pistol)A second pistol design was the Wildey, which was sort of an afterbirth of Automag, and I believe that was chambered for the 45 Win Mag too.
http://www.wildeyguns.com/wildey.htmlHowever, neither of these pistols ever shot the 45 ACP, and the only gun that could have done that was the LAR Grizzly.
https://en.wikipedia.org/wiki/LAR_Grizzly_Win_Mag It was a scaled up 1911, so some 1911 parts were compatible and some weren't. If they had separate mags for 45 ACP, that's news to me, and it would have taken a lot of farting around to change out the recoil springs and scale this down to plain old 45 ACP. It must have also required a different barrel to shoot 45 ACP, or some sort of chamber adapter to account for the difference in headspace. This beast was also chambered for the mighty 50 Action Express, which at the time was around in the big 50 Desert Eagle. Now, while the Desert Eagle is a big MoFo of a gun and can shoot 50AE forever, it was a dismal failure in a 1911 platform and all the 50 LAR's are long since broken or blown up. The 45 Win Mag was less powerful, and therefore these guns survived. The company that made them, however, is LOOOOONG gone, so your buddy is out of luck. Best he can hope for is that somebody has broken LAR in 45 Win Mag and has a magazine to sell.