I have an old Mecablitz 106 which I restored,in fact I found another which is in better shape than the one I bought originally in Germany in the early '60s which I am restoring as well but the gist of my reply to you is that I contacted Metz with a query about it,specifically where to obtain the cells for the power pack and they did reply to me with a .pdf file of the schematic and parts list which was a great help with the restoration.Those coin cells were made by Varta and are no longer available from them and if you do find any,assuming that you need them they likely have passed any useful life in all likelihood.
Yours might be new enough that they will have just what you need.Good luck with it.Ron G