Take this with a big pinch of salt because I haven't worked on an Alpina/Castor in a few years and my memory is faulty, but the chain brake mechanism used on 80's Alpina's was used literally unchanged until 2000 or so on Stiga branded chainsaws (Alpina, Castelgarden, Mountfield etc have all been absorbed by the same holding, first called IGP and now Stiga) so it may be worth paying a visit to a Stiga dealership and have a chat with them.
Stickers however are another matter: that stuff is simply not available anymore. You would probably be much better off having them custom made by a graphic studio, just be sure to get the measurements right and to take high quality pictures so the colors are as close to the original as possible.