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...I do this repair here. Last time I checked, you could still get RH threaded helicoils (the ones for older spark plugs, when you strip the hole in the cylinder head.) But it varies with manufacturing trends, and there might now be someone making and selling the RH/LH sets again out of Asia.

OTOH, the tool set for overboring, rethreading the hole, and installing something called a "threadsert" (which appears to be stamped out of sheet metal) are readily available from a couple of sources, The threadserts themselves cost about six or eight bucks each. When you buy the tool set, it comes with a few sets.

It's not an hugely difficult job, if you remove the crank from the bike, hold it in a vise, and pay attention to getting it at a 90* angle to the crank arm. I'm sorry, but I don't do it for other people any more.I find working for other people to be a painful exercise in patience, which I have in short supply these days.

So I guess it depends a lot on the value of your crankset. I have a lot of older ones to which I am attached.