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I bought a genuine Hasselblad deluxe 1.5" wide strap for my 501CM from KEH which I am pleased with anyway. I previously searched like you but got told (right or wrong - I have no idea) that the camera body fitting is a proprietary fitting, so none on the aftermarket.
I have made lots of camera straps to my liking by going to a leather supply shop and picking up straps and useful scraps for things like neck pads. Tools that are useful include a hole punch, a rivit setter, and a good sharp blade for trimming the leather to shape. It sounds as though you might have a Hassy strap you don't like. You could just reuse the camera attachments in a homebuilt strap. Often I install sturdy plastic snap devices (available at most hardware stores) near the ends of the strap so that I can quickly remove it when the camera is on a tripod. Of course, the formidable prices of even used Hassy straps may make you think twice about dissecting one to make (or to have made) a strap more to your liking, but it is a heavy camera to use feeling discomfort around your neck or shoulder.
Check out OP/Tech, they got a "Super Pro Strap" with fittings for Hasselblad at about $20 from B&H. (You'll want a type A strap to get the right connectors) I got a similar strap for my Nikon, I love it. They say it halves the apparent weight of the equipment and I agree, it really does feel less heavy.