Take one rusty/failing powder coat clothes airer,

- Missed from the tip trip
Chop off a bit, bend

- Plus deburred
Just the ticket
Noticed the tensioner quite stiff, so removed to lubricate it.
Then noticed someone has been here before.
Spot the odd one out, even easier once removed!

- Close enough!? Well, it is M8 so at least that's correct
Decided (having lubricated tensioner) to go for three matching M8 with 13mm heads (plus thin washers) and a spot of thread lock on each.
Strangely there's two tensioners on this belt, both sprung, one either side of the alternator. Guess something to do with the Start Stop (as think alternator may also restart the engine??) which would change where belt needed tension (after crank pulley or after alternator)