which make (Bes or Opacmare or, eek, Cooney)? And which country is it in? (if it's france or UK, I might be able to help, but not otherwise)
(I appreciate you are asking for source of info, not a servicing firm, but I was gonna suggest the local firm to buy oil and sparss etc from and then if you find the helpful individuals there they will offer free advice at the same time)
Eek, never heard of them. If (as it turned out) you are in UK, I was going to give you the contact details and name of the Besenzoni agent in North London, very helpful people. But never heard of your make of passerelle, dont know where you would get help with it, sorry ....