Knowing what others like prarieguy have experienced I didn't even bother looking around when I found myself in the same situation.
I had a magazine kicking around that I decided to use. Exactly what it was from, I don't know, but it was very similar to the mag from a Lakefield mk2 but just shy of being interchangeable with it.
I had to move the mag position rearward to work in the NAACO. This requires lengthening the slot in the floorplate and making a new guide and latch. I just made a whole new floorplate because I didn't want to alter the original.
The original floorplate had a brazed-in filler in the aft part of the mag slot. As well, there were 2 locating cuts in the bottom of the receiver that would be anchor points for the rear foot of the mag guide. My feeling is that it was done this way to perhaps accommodate a 22 magnum version .
Although the cuts allow for different positioning of the mag guide, the screw hole position in the guide is unique to the particular version of the guide.
I made a new guide and spring. My conversion works reliably but was a pain of a job. I did it for the fun of it. Be prepared for a whole lot of tinkering, remaking of parts, testing etc, etc. There was cutting, forging, fitting, and heat treatment involved.
Positioning and geometry is important and you have to sneak up on it, which takes time
In a previous discussion on this forum it was mentioned that others have done this type of work as well. There's more than one way to skin a cat but it is ultimately up to the individual to decide whether such work is worth doing.