I don't understand why he won't give you the prescription. What difference is it to him how you pay for it?
Not knowing where you are it's hard to give concrete answers on where to get meRAB but I would offer the following:
Your county health department
Your local charity hospital
State assistance for children with no insurance (we have that here in AL)
Ask for a freebie sample from your doctor
Purchase - with prescription - from a Canadian pharmacy (I get my Flovent from Canada as it is cheaper even with shipping costs)