Well, that's some narrow but conflicting criteria. Not bigger that .41 mag, but you want a .45 Colt?
Assuming the smaller than .41 and no I, K or L frames are accurate, that leaves you with an N-frame .357, or a J-frame.
Since you already have 2 M28s, I agree with Stainz, a 27 or 627. Over .41 caliber, I'd want a .45 ACP for the full-moon clips. But I'm just not a .45 Colt fan.
Have you considered a post-1960 22/32 or one of it's descendants? That's the only J-frame that would interest me.
What would really set my propellers spinning is a 610, but they're pretty pricey.
P.S. after reading your last reply, I don't think a .45 ACP would be easier to find than an LC, especially if pre-lock is a requirement. As I said, I'm not a .45 Colt fan, but I do regret letting my cased, nickled 25-5 get away (sniff, sniff).