I know this must be discussed somewhere, but I apparently am not smart enough to figure out good search terms.

Basically I need a very wide enlarger lens, something on the order of 35mm or 28mm is what I am thinking.

I have two objectives. First, the driver for right now, is to print some extreme enlargements of details from some 60 year old wedding negatives. For a few family members these are the only existing photos, and although the quality will be poor, it's better than no picture at all. I can't get those folks to sit for portraits now. I'm using a Beseler 45 with a 50mm lens backed all the way to the top, and I can just barely get the framing I want in 4x6. But I want 5x7. As I said, this is important to family, not for hanging in a museum. (I know I could turn the head and project on the wall, but that would require moving some equipment, and I would rather not do that unless a decent lens costs too much.)

The second objective is to start experimenting with some of the old 16mm film formats. I picked up a slitter - and so far haven't lost any fingers on it - to make film for their cassettes. Making a mask is a piece of cake, so I'm not hurting for a carrier. But I can imagine that to make decent size prints - grainy or not I don't care - will take a wider lens.

These focal lengths are not only hard to find information about, but they're hard to find, even on eBay, the junkyard dumping ground for the whole world. The few that I see seems rather pricey, but this may be an artifact of scarcity.

Can you kind folks give me some advice, first of all about what is available and the relative merits of various selections, and second what seems to be reasonable prices for these pieces, please?

My current lens collection consists of Nikkor 50 and 75, and a Schneider 150.

Another thought I had was to find a decent M39 (or M42 is probably cheaper) 28mm camera lens, and just use that, although there may be issues with field flatness. I'm not enough of an expert to know how well that would work. I suppose it's no worse than using your Speed Graphics with a light back as an enlarger. Is that crazy, or reasonable? At least it would give me a lens I could also use on a camera body.