I would call around and seek other vet's opinions on this - 2 months without end is a LONG time for a girl to be calling. It can be quite dangerous to her health to be in estrus this long without being bred. Many vets dislike to spay when a female is in cycle because of the slightly higher risk of bleeding. But there are many who are willing to take the extra precautions to minimize that risk - call around and talk to a few more in your area.
As for what to do in the meantime, there are times when my Lexus is in estrus but it is not appropriate to allow her to breed. So, until I feel it is safe to breed her, this is what I do:
I use my bedroom as the confinement area. I move the litter box, food and water dishes and any favorite blankets, toys, scratching post/condo in there and I close off the drapes so that it is very dim but not totally dark during the day. At night, I do have a small nightlight on my bedside table, but it is only a small bulb and not much light. I close and cover the heating vent so that the room isn't heated. (It never gets actually ~cold~ in there, but it does stay about 10 degrees cooler than the rest of the house.) Since my desk/home office is in there, I am in with her frequently. I guess I've been lucky as I have had some small success with it.
The dim, cool room simulates the time of the year not normally associated with female cats experiencing estrus. If you can get the environment close to that time of the year what with light and temperature variables, you may be able to reduce her symptoms somewhat until she comes out and the vet can spay her.
I hope this helps at least some ... as someone who has a breeding SIAMESE female, I know how loud and annoying it can be. *wink*