We have been users of classic 1970s 35mm SLR systems for almost 40 years in our household, mainly Canon and Olympus, with some Nikon, as well as M42 gear before that. In terms of lenses, in addition to FD Breechlock lenses we also use some classic/specialist M42 and Nikon Nikkor AI lenses on the Canon cameras with Canon original adapters N and P, as well as newer Chinese made clones. As for Olympus and Canon, our lens systems are largely complimentary, e.g., fast long toms and extreme ultra-wides on Canon, everything in between mainly Olympus OM.
We used to have one OM to FD adapter - purchased a long time ago - but this became worn out a while ago. Sadly, we have been unable to find any more anywhere. (This saved having to carry both OM and Canon bodies in many circumstances.)
There are plenty of lens mount adapters available for almost any conceivable lens mount to Canon EOS - and many others - which has a longer flange distance of 44mm than FD mount Canon at 42mm. So from a technical perspective, it is actually easier to produce adapters to FD mount than to EOS mount, with an extra 2mm "to play with".
Would anyone else be interested in perhaps having an adapter/s custom made? Easy enough even for a small engineering outfit with CAM/CAD and CNC mill etc. We would certainly be more than interested in at least a couple of OM to FD adapters, but there are of course also other possibilities such as Leica R to FD, C/Y to FD, or PK to FD. Even 10- or 20-off of any one type would, obviously, make them a bit cheaper, and a hundred + even more so.
