And then snapped the thread cutter in the hole I cut.
Not going well.
Where can I buy a new LH crank arm?

Wanted ad on here. Left hand arms are available but expensive. It’s probably cheaper to buy a chainset and eBay the driveside

JE James do them. My local LBS TY Cycles in Chipping Norton do too

How old is it? Buy a crankset and you have some spare rings

I’ve just swapped the cranks on one of our bikes so have a 170mm SLX crankset (no chainrings) surplus to requirement. They’re M7000 – were used as 1x but I *think* the same chainset can also be used as 2x (certainly has the drillings for an inner chainring. Let me know if it’s of interest.

Is drilling the bolt out not an option?

Not if there’s a broken bit of easy out or tap in there its not!

Think I’ve got an 10spd SLX crank in the garage, seem to remember at the time I got a deal on buying a whole new set instead of chainrings.

What length / colour ?

Just checked, yep 10spd, 175, in black/silver SLX

Tiger YHM

I’d have a go with a drill from the other end if it were me.