Rip your CDs and put them on a flash drive.
Have you considered an older model boombox,
from Sony or Philips?
1) some have multi-disc option
2) good size/sounding speakers, placement flexibility
3) enough weight and stability to produce good sound
4) possible plug to cigar lighter or battery operated
5) modest cost (internet or garage sale)
You may want to get familiar with the features of a unit indoors
before graduating to the car.