Yeah shelby is the brand. Found them online. Thanks.i know the jack your talking about. it ahs a bracket welded to the tong and pipe with a groove on the out side lip on the pipe. the jack slides on and rotates forwad and back and i held from sliding off the pipe by a 2" or so snap ring.
not sure where you are. farm and ranch and also utility trailer supplier. we have one similar to that one a snowmobile trailer. shellby is the brand name on that jack. it uses a cap screw in place of the snap ring though.