There is this kind of stuff:
https://evea-kartmasters.fr/fr/relais-de-puissance/2144-module-pre-charge-12v-zeva.html
Don't know exactly were they find it, or even if they produce it themself, but it seems to be designed exactly for what you want to do.
Explanations are in French, but it's simple. Whey you turn the key on, it charges your controller and wait for voltage to be equal (or almost) on both sided to close the main contactor.
EDIT: The datasheet is in english, I posted it bellow
https://evea-kartmasters.fr/fr/relais-de-puissance/2144-module-pre-charge-12v-zeva.html
Don't know exactly were they find it, or even if they produce it themself, but it seems to be designed exactly for what you want to do.
Explanations are in French, but it's simple. Whey you turn the key on, it charges your controller and wait for voltage to be equal (or almost) on both sided to close the main contactor.
EDIT: The datasheet is in english, I posted it bellow