Almsot any doc can write the script for you.In fact, that is how my doc is doing it. He writes it and I go pick it up and then make arrangements for him or someone in his office to do the actual injection. I could do it myself but it is their policy to have it done at the office. Money Money Money!
You might check out the Planned Parenthood in your area. I went to them for depo shots for several years. It was about half the price I pay now. For the first visit you were required to have a yearly exam with them which was around $40-$50. You also paid $50-$60 for the injection. After that you paid only for the injection, no fees for the office visit or anything. It was a deal. You also could change your B/C method during this year if you wanted or needed to and they provide most everything at a reduced rate. The nurse practitioner at our PP was more thorough than many doctors I have seen.
Anyway, if it is RX'd I believe you will pay around $90 at the pharmacy for the medicine. Be sure not to rub the injection site after you give yourself the shot as it can rupture the little beads of medicine prematurely. You do not want that to happen!
As far as OP's writing for depo I have no clue but it may be available from some of the IOP's.
Good luck!
Peace-