Yeah, I suffer from this too, although not to the degree it sounds like you do. In my case, it's mostly because my skates are too tight up front. It's a lot better now that they've been punched out, but still not gone.
What kind of socks do you wear? Its counter intuitive, but it's possible that you have too much material in the boot, so there's no room for air, which can act as an insulator. This is why you hear of barefoot skaters who don't get cold feet. Maybe try a thinner sock? I skate in knee-high nylons, for example.
But synchro is definitely the worst in terms of being cold. My team does a lot of standing around and listening and it does get cold- my heavy polartec never comes off. Do you have enough room in your skates for some hot hands, or those things they make for skiboots? That would get pretty expensive though, since they're single use. Once upon a time, they used to also make heavy boot covers....my memory suggests they were made out of a faux shearling type material. They were all the rage when I was about 7 and nothing but class (we're talking early 80's lol) they may have even had pompoms on them. I don't know how much something like that (in an aesthetically improved model, of course) would help though, and tbh I'd be worried about someone's, including my own, blade getting caught.
Another thing we used to do.......in the days loooooong before heat-moldable boots......was to line up our skates blade up on the floor heater in the warming room. Our patch skates were nice and toasty by the time freestyle was over, and vice versa.... I'm not sure I'd advise doing this with heat-moldable skates though.
I dunno.....you're not alone! Hopefully you'll find a solution!