The bicycle repair business suppliers make pedal thread repair kits ...
2 kinds a sleeve threaded on both sides the stripped hole is reamed , then tapped, then the insert goes in
And Helicoil .. a coiled diamond shape steel wire,, similar process..
Your local shop unwilling to do that, don't own or wont buy the tools to do that.
take the crank off ,
mail it to a shop that is willing to do that, owns the tools , etc..
VAR , France, makes this one..
helicoil type
...