Glimmer of hope...
Vivitar Ultra Wide & Slim + Redscaled Expired Kodak Gold 200 + Salt Soak.
Salt Soak. (My thanks to fiona who first inspired me to try this, quite some time ago now.)
Add 3ish parts BOILING water to 1ish part salt.
Put developed redscale negatives in the mixture.
Stir gently to ensure maximum solution coverage.
Leave for 10 mins or so.
Fish negatives out & hang (or stand) them where they can dry.
Carefully wipe off salty debris from glossy side first.
Gently wipe reverse side to free it of excessive salt residue, but take care so not to lift emulsion or scratch it excessively.
Basically this involves taking a roll of ordinary 'bog standard' print film, reversing it and respooling it into another film cannister (all done in a dark bag) so that the light is exposed on 'the wrong side of the film' when you take a shot. You then lose two 'stops' on the optimal exposure conditions from the original. It gets developed in exactly the same way as print film, but be prepared for the technician to be a little startled (at best) or a little irritated (at worst) when they realise that something very odd has happened to the film. :)