Homebuilt porteur rack v1.0

That makes sense. Do you have rack mounts on your fork, or are you mounting to the axle like the Cetma/VO racks?

I might buy a drill and have a go myself. Seems like it'll be a lot cheaper

My steed is a Cinelli MASH, so no, no mounts at all!

I am gonna try a few things for mounting it, there will be axle mounts like the VO rack yes, but that also requires a brake drilling for a metal strap to stop it rotating back or forwards, so possibly an adjustable stem clamp, or rubber lined P-Clamps mounted to upper forks will work.

One thing I will say about having a go yourself is that precision and patience is key to this, also buy extra materials like I have, so that if during fabrication you screw it up, no worries as you still have loads left to try again!
Always double check your measurements, and make sure you have a good full sized hacksaw (no junior hacksaws!) and a few spare blades and a good bastard file.