Hi, a trailer winch is not a bad idea if you are on fresh water. You could mount it somewhere under the rear deck (maybe above the quarterberth) to get it out of the way (those things are bulky and would be dangerous in the cockpit where the original was mounted. Or just use an ordinary winch with a rope pennant instead of the ss cable. If you have a REALLY old M24 with the bronze CB, it weighed a few hundred pounds. If you have a "newer" M24 (1967 or later) it's probably a fiberglass CB, which only weighs about a hundred pounds.
As far as getting a real "centerboard winch", that's going to be a needle in a haystack.
I kinda miss my M24. Have a Columbia 24 now.