Guys, sorry not to have replied sooner, so busy with the moving out (and staying in hotel until the start of the trip), the last 2 weeks at work after 8 years in the same company = handover mess, + an unexpected trip to France last week....
Thanks for all the help and the offer, it's really appreciated.

I'll try to taobao it thanks to humanbeing chinese, if that fails, I might take you up on your offer TB-racing !
From what I was able to dig on the mighty net, it's supposed to be a 120mm ring for the rear shock setting on the YBR250, so that'll be what I'll be looking for on taobao.

Will keep you posted, thanks again !