Does anyone know a company that could make me small quantities of a double walled tube? The first (inner) tube to be 1.5-2mm wall, clear resin with a single layer of 80gsm woven glass fibre (preferably as close to the inside of tube as possible), the outer tube to be “normal” carbon fibre with standard 1.5mm wall and the outer diameter to be 25mm.

Odd request I know...but then I did say I was the mad scientist...

600N is quite a load for a 25mm rod including bending and torsion. If the light should be opaque anyway, a solid grp tube might be enough. After you cut out the design, give it a laquer finish, and the cutted grp should become translucent again.