Lindahl 17.0910 trigger flash bracket for Hasselblad. Fits fine on my 500c (as shown); should be fine on other 500 series. Cold shoe.
While this works OK with WL finder (I find the grip angle usable, but a little bit awkward), it's best with an eyelevel finder - either 45 or 90 degree.
$40 plus actual shipping. Shipping weight is 2 lbs and it ships from zip 56465. 10 day return privilege, buyer pays shipping both ways.