I have to replace the window for the heartrate monitor on the back of a smartwatch.
It's supposed to be IP68.

I can get the window, but it doesn't come with the adhesive.
It's clear that what came with watch originally was a black very gummy gasket-like doublesided tape. But it was also very thin.

If I am to source tape, the circle I'd have to cut would require 2cm² of tape.
Can anyone help me out with product names or search terms?

Alternatively, would a different type of adhesive work better? i.e. Not a tape.
Looking online, I've seen a few of these watches on ebay with damaged or missing heartrate windows. I've got a few laying around, a couple types of LOCA, some e6000... and misc other types.

Thanks in advance for any advise or suggestions you can provide.