At the risk of restating - filmcapture has the right item at B&H (maybe you can't stand the exorbitant price tag, which I agree!). Maybe the Cambo plate is cheaper. I have the Hasselblad adapter plate and use it on a Cambo wide DS and on a Toyo vx125, though not looking to sell it. As filmcapture says it does the job, though not amazing (esp. for price) and will go on any graflok 4x5. You can use your regular 4x5 groundglass with marks as this plate positions the sensor in the same focal plane, or get the Hasselblad focus screen plate made for 903/905SWC Superwide bodies. Can't seem to find it at B&H right now, but can often be found on ebay. Use a chimney hood or I've found a Hasselblad PM45 Prism 45deg Viewfinder handy as well.
Good luck.