If the Zeus BCD is actually 120 then you are in even better shape, just buy NOS stronglight 122 bcd rings from harris cyclery (France is right next to Spain!) and I can vouch as a recent customer that my modern stronglight 122 rings said NOTHING on them other than "38T" and its simpler to file a higher-bcd ring to a lower bcd (as Jerry Moos Points out) then to go in the other direction.
This is a recommended and successful solution for Nervar 128 bcd cranks - buy 130 mm shimano rings and ream out the holes for 128 bcd cranks, with a 1 mm gap all the way around the spider.
Some day I'm gonna manufacture a 5-arm ring with a bunch of score marks - one for each BCD - and a bunch of cross hairs - one for each chainring hole - a file-it / bore-it-yourself-er - that will work with any crank !
We can call them "X-Rings" !!
- Don Gillies
San Diego, CA