Hi,
there are step down (buck) switcher circuit ICs.
Look for one with duty cycle of 100% to get 12V output form 12V input.
Also look for one with current limiting feature.
Many semicondoctur manufacturers produce this ICs.
Each manufacturer should have an interactive selection guide to find a suitable IC. It is free to use. Please do so.
Additionally many distributors have those selection guides, thus you are able to compare between different manufacturers.
Klaus