@didier nerd-sniped me… the sole hard copy I could find is only available for loan in a library in Germany (see WorldCat). As for a digital version, this website claims to have it (haven't verified, it's downloadable after registration only):
Commodore Software - Commodore 64 Whole Memory Guide
Commodore 64 Whole Memory Guide is much more than a memory map. Instead of just giving memory locations it gives you a detailed description of each location, ...
(commodore.software)
(It's not on archive.org or in any of the shadow libraries)