I did this MANY years ago. Celled a repairman who welded in some
specialized plastic stuff (looked like a big crayon).

There's a kind of two part epoxy (can't recall the name just now) that
comes as a long thumb-thick cylinder and has inner and outer layers
(presumably with some neutral separation layer). You cut off what you need
and then kneed it thoroughly to mix the two layers and will begin to set.
I don't know if that would work but it might. There may be special
materials available for this purpose.

Anything that can withstand the pressure could work. I once had a Honda
Prelude that had a crack in the high pressure liquid line. Still under
warranty but the dealer had to order the part. While waiting I put a piece
of rubber hose material over the crack, put a hose clamp over it, and
recharged the system. Even I was surprised that it held but it did and
kept me cool until the part came in.

Special sealers aside I don't know what would work in this situation. Is
the evap made of two layers of thin aluminum close together with bulges
stamped into it to form refrigerant passages? Is there a way you can pinch
down on the affected spot without destroying the passages? Maybe a piece
of rubber (of a type that stays resilient when cold) over the hole with
some sort of jury rigged clamp arrangement applying pressure?