Good morning, Mirko;
OK. Metz 60 CT1. Honeywell-Heiland Strobonar 600, 700, 800. Nikon SB-1. Almost any of the handle grip or bracket mounted large electronic flash units from the 1970s.
However, you can use one of the electronic flash units with an integral light metering auto mode, such as the Vivitar 365, Sunpak 522, 544, 622, Honeywell-Heiland 770, 882, and several other similar models. They do think the world looks like an 18% gray card, but they do not rely on any TTL light metering or other communication with the camera; something the Kiev 88, 88CM, Hartblei, or ARAX will appreciate. If the negatives you get are not what you want with a particular electronic flash with an Auto mode, adjust the ASA dial on the flash to get the negative density you want from that flash.