I drilled small ~ 1/8" horizontal holes in the stand-offs on the rear of the case, with the holes parallel to the back of the case ... so no
penetration of the case is made (thus no sealing needed) ... then just ran some small gauge wire through those holes to attach the case to the nearby display items. Worked great and those wires are dirt cheap and you can attach the wires to anything (a pole, a tree, a t-post, rebar, a stand).
I literally did this out of haste (and for raw speed of installation, since it was snowing and about 0 degrees before windchill) ... but in retrospect ... I'd always do it this way again ... super easy, dirt cheap, fast and flexible. Toss the wire at the end if you want.