Can anyone tell me what thread size the bolt that holds the cleat that clips into the handle bar mount is?
This bit

countersunk and pretty wide-headed, marked YFS 010.9 FWIW
Thread dia is 5.9mm on my cheap calipers
Thread length also about 6mm, might be a coarse M6 – doesn’t look quite “normal”; total screw length 10mm

Noticed on mine the top has rounded out over time and they seem to work loose over a winter too.

Sure exposure could tell you (maybe even send/sell you a spare). In fact I might ask for myself as you’ve reminded me mines looking a bit tired now.

As a spare with the cleat it’s £6

Exposure Spares

Sorry just realised that’s linked in your op.

I guess since you don’t want to spend £6 that you are looking for another source.

Thanks for the replies.
I’m trying to see if it will fit my full beam light which had an M5 thread.
The plan was to replace the existing 31.8 bar clamp with an exposure 35mm bar clamp & cleat (new bike has 35mm bars).
It looks like it’s not going to work😕

The cleat isn’t threaded.

Trying to follow exactly what you’re saying but I think you are looking to retrofit the cleat to another brand of light.

In which case if you could shim the bolt hole in the cleat and get a shallow headed M5 bolt then maybe it could work?

Dinghy chandler’s often carry lots of packs of different sized stainless bolts (someone like TridentUK will probably do them mail order).

Yeah, trying to retro fit the cleat to another brand of light.
I was hoping it would be a straight bolt on swap. I’ve plenty of M5 stainless screws of various head types so might give it a try.

Universal 35mm bar mounts seem thin on the ground.

Did this with my Halfords light, used a shoe cleat bolt with a washer between light and cleat so as not to puncture anything in the light. Solid as a rock so far.