Rear mech. What size is the thread?

[slowmotion]

These people do an M10 x 1mm bolt for not very much but you might want to take a hacksaw to it to cut it down in length........

https://www.ebay.co.uk/b/M10-Fine-Pitch-Bolts/42905/bn_7023538356

£1.94 posted.

 

[Darius_Jedburgh]

I found this, and it has a hex socket for easy removal.
https://www.accu.co.uk/en/flat-head...2EtXK56vF0NRieZ24fGDQzJOkjmuwdPhoC1EkQAvD_BwE