cowl/kick panel vent rust - need some ideas

[71c10longbed]

After a 12 month hiatus, I am back working on my rusty cab. All rockers(inner/outer), cab supports, and some of the floor has been replaced. Cab corners as well.

Now I am into the more difficult stuff. I've patched a couple of places on my "inner cowl" around the heater motor. I cut a hole in the bottom of the passenger side just to check. Massive mouse next and once that was vacuumed out I found my old friend rust. I really don't want to replace the whole cowl panel due to the labor involved and looking at the patch panel I don't think it will solve my current issue. I've post a picture and the rust is on the inner inner cowl panel where the vent door mounts. I can't find any patch panels for this.... thoughts/ideas/prayers?