I have struggled to find anything around, except antique Fremch cast iron clockwork roasting spits you can buy for like $1500. I want a sturdy clockwork device that could drive a roasting spit - not an electric motor.

In my head I imagined you could buy a low gear clockwork device working at maybe 4-6 rpm, that you could wind up and leave ticking. I love outdoor roasting but sitting someone next to the spit constantly is exhausting, and an electric motor needs batteries or an engine using fuel, neither of which appeal to me. Im looking for something faitly small, that could easily be put in a backpack or carried with one hand, tough enough to turn a spit with several kgs of meat on it (no plans for whole hogroasts at this point).

Can anyone with any experience with clockwork, antiques, or this kind of thing help me? Thanks