It sounds as if you are leaning towards a new production freewheel as opposed to vintage ones.

If it were me, I'd go for a vintage Shimano 600 or DA UG 6-speed or a Sachs Aris 6-speed. With that said, since the spacing is 126mm, a 7-speed might fit (sometimes they do on vintage hubs and other times they don't until you respace and re-dish the hub).

I could have serviced freewheels which fit your needs. If interested, PM me and I can send you pictures.