/diy/ - Do It Yourself

hey /diy/, I need some ideas or products to solve my problem.

I made myself a acylic glas plate as an insert in a window (the window itself is open) so I can make an airtight ducting for the AC.

now I have different options to push the acrylic glass plate onto the sealing but Im looking for a nice looking and save way.

the best option would be 'inverted' clamps (with a spring) to constantly push the plate on the rubber, like the arrows are indicating.
but I cant find proper products so far.
any suggestions?

another option would be to use a threaded sleeve and a screw on both ends (on thread inverted).

any general ideas how to fix it?
good-looking, secure-fitting and inexpensive solutions are preferred.