[lifeofbrian]

I have found a few places but all have very little choice, and no button head/cap head for my XC frame. Red or oil slick would be tasty.

 

[EdSawyer]

probolt ?

 

[JDUBku]

Betterbolts.com - Have fun

 

[gasguzzlingV8]

Watch out for Stainless bolts that are Ti coated.

 

[Aglo]

Both Uberbike Components and Superstar Components have what you want and both are UK brands.
Direct links for theirs titanium offer:
https://www.uberbikecomponents.com/category/362/Titanium

https://www.superstarcomponents.com/en/shop/mountain/mountain-titanium/

Uberbike has a bigger selection on oil slick.

 

[milehi]

RaceTi. I think they're in Leeds off the top of my head. Great prices too. I ordered yesterday and they're already in the mail to me in Southern California

 

[aussie_yeti]

xcracer.com