I am also looking for this bracket. The supplier three in Austria also has a stand I have not found anywhere

Our supplier could not find the window bracket and it seems that it is not sold separately, at least not in our region.
Therefore, we cannot include it in our range. We are sorry that we cannot give you better news.

Oder diese Fenstermontage:
(lowcostmobile ZTE MC889 5G Outdoor-Modem)