Plagiocephaly (flat head syndrome)

Hello parents! I’m a first time mama in need of some advice. My son is 3 months old and has a flat spot on the back side of his head. He’s currently in repositioning therapy but hasn’t seen any improvements for the last 3 weeks. I worry that they’ll suggest a helmet. I frankly can afford a helmet and it isn’t covered by insurance. Plus it would be so hard to take the one day a week off work plus my other appointments. Please let me know if you went with a helmet? Didn’t? Or any advice for me going forward? Thanks!