“Buck Convert-e-r”
I suggest you look at the Inland DC-DC Voltage Step Down switching converter module. Input is 3 - 40 VDC, output current up to 3A, precision Vout adjustment via multi-turn pot. Micro Center has these for near $7, their designation is K98R.
I think these may go into continuous conduction so voltage drop can be minimal (module is TI LM2596 switcher based).