3rd Ultrasound

I see ladies posting on here pictures of their babies in the womb during the third trimester and I'm wondering how can I get another ultrasound!? My doctor refuses to give me a 3rd ultrasound because everything is going good but I still wanna see my little one, one more time before he comes....anyone else only allowed TWO ultrasounds during their pregnancy? One to determine how far along you are and the other to determine the sex.