I know, I know, it's not .45 ACP (but a SIG P220 isn't striker-fired, either.), but my favorite, thus far, is a Glock 38 -- same general size as the Glock 19 and 23, but the softest shooting .45 I've ever owned. (I've had no problems finding ammo, and in bulk, its generally about the same price as .45 ACP. SD ammo is expensive, no matter what you get.)
I shoot mine better than my Glock 35 (.40) or my M&P Pro in .40... which surprised me when I found out.
The GAP Glocks can be found very inexpensively, and if you ever find that .45 GAP is no longer available, you can use a 19 or 23 slide (with only minor changes.) I think .45 GAP will be around for a while, even though only Glock supports it. If I find one cheap enough, I'll get a 37, too. (I paid $350 for my Glock 38, new in box!).
My only change was to install a Ghost trigger kit.