I'd just get my own vet out to do an exam and fight this battle later. Don't you want your own vet to have a look at the horse?
Wondering about the insurance company accepting a PPE report, though. When I insured the company had a form. They want the information they want in the format they use. This info in this box with these signatures.
Just keep calling the vet's office, and I'm sure you'll eventually get it from them. I had a similar situation with an out of state PPE exam, except the horse I was looking at didn't pass. The only reason I wanted a copy was because the seller was trying to tell me she wouldn't return the deposit I put down to hold the horse until she received a copy of the written PPE results. I got my $ back anyway, but I still called the office constantly for the written results and no joke it took about 2 months to finlly get it. I didn't feel like the vet was being sheisty or anything, I think she was just very busy and may not have ahd the admin staff to print up the written results. At this point maybe you can get them to post date the report some since it has taken so long? Maybe not what your insurance company wants to hear, but I am a health & life insurance broker (human not equine) and I don't think that would be a big deal under the circumstances.