Alternator bolt required

[Draught-LHM]

Hi,
I'm trying to replace the alternator belt idler on my 1993 2.0 Sei Turbo Mk1.5, 45k miles, but the only ones available on part number 57521 have an M10 mounting female, my car has the original with an M8 female.
There seems to have been a reliability issue with these so Citroen increased the bearing size and mounting size. This was standard on all MkIIs and were modified upon replacement on Mk1s.
The mounting is combined with the lower long alternator bolt which has a 22? spanner size and projecting from the head is a stud for mounting the idler.
I need the later type with an M10 (17mm spanner size) stud. A quick check is to screw on to it a 17mm spanner sized nut.
It's my belief that most of the XU and XUDs in use will have the type that I'm looking for.
Im getting desparate for this as it has now gone noisey. I have the idler but can't fit it without the correct alternator bolt.
Any help with this would be greatly appreciated,
Thanks,
Chris

[Draught-LHM]

Hi,
Did I include too much info!
I simply need the long alternator bolt from any XM except the V6s, also same on a Pug 605.
Hope someone can help as this has put my 45k mile 2.0 Sei off the road as I cant change the idler.
Thanks,
Chris

[Draught-LHM]

Here's a drawing, the original is still on the car

[Draught-LHM]

I would estimate the lenghth of the bolt to be 14 - 15.5 cm, 5 - 5.5"