In California you have to write a letter and make the request in writing and specifically ask. Document - Document - Document and keep a records of day, time and who you talked to and what was said. They are not suppose to refuse you. Doctors & hospitals tend to want WHY you want them and if they get just a little sniff something is wrong then they alter them and clean them up, lose them, misplace them, their in archives and can't find them, etc. Doctors have a brotherhood and tend to lie and cover for each other. I'd be careful in asking another doctor to ask for them. You have to be careful in how you get them.
Offer to pay for a copy of the x-rays and you may also have to pay for any copy costs. Ask how much and be prepared.