This page is about scratchbuilding an 8 kW generator but it is to be used for a Flakscheinwerfer:
Maschinensatz 85V 8 kW
This thread claims that the Uhu used the same generator as the Flakscheinwerfer:
Quote from the link above:
"The removal of rounds from the Panther was not to accommodate the extra battery but for a stand that held the GG400 generator used to charge the extra battery the tank carried – the same as the command versions.
The UHU was not full of batteries but was full of the 8Kv generator set which was the standard gen-set for the 60cm searchlight in Luftwaffe use. The UHU used the standard s/l and gen-set just with an IR filter over it."
The GG400 is, or at least was, available from Riich:
Edit: For those who haven’t checked the link about the generator for the searchlight.
The Uhu worked together with IR equipped Panthers and the Panther needed a power source to power its own IR equipment.