Finding out gender

So my doctor just informed me that my anatomy ultrasound won't be until 21 weeks!! Ugh! We thought we were going to find out gender at our 18 week appointment in 2.5 weeks instead of 6 weeks. My husband said he doesn't really want to spend $50 to go to Tate diagnostics to find out the gender because we get it for free at 21 weeks. I'm disappointed, I was so excited!!!! Any tips or advice you can offer? Idk if I'm being selfish, he's just as excited but just doesn't think it's necessary.