Posted By Thomas Bennett
I’ve seen these referred to as a "shoe" where the foot of the finder bracket fits into the shoe mounted on the telescope. The shoe for my Orion finder is a fairly common size but about half the size of the one in your picture. If yours is a non-standard size, your only shoe source may be from the manufacturer of the finder bracket. Other options might include buying a set of standard rings with shoe included that fits the finder, or drilling holes in the foot that corresponds to mount points on you telescope.
The finder looks kind of heavy so taping the foot to the scope ala Telrad/Quickfinder securely may not be possible.
Good Luck - Tom