well if you come down to southern NY, like an hour north of the city, I would gladly make you some custom footbeds. I have a pair myself and they are absolutely fantastic.
at my shop we have a cheap model thats not custom for like $50, and nice one thats about $90 and is slightly moldable, and then a fully custom (which i have) for about $150.
but otherwise, there are tons of bootfitters near mountains in VT and all that, and i've heard the Ski Rack is good too, i think its in burlington if im not mistaken.
or, possibly your doctor can make you some sort of orthotic
i have one, its a white piece of plastic that is about half the length of my foot, fully custom, like made from a cast of my foot, and absolutely amazing. i got them because i had arch and knee and back problems for a lot of sports, and it was sick because they are like $400 but they were completely covered under insurance.
the only thing is that they arent really meant for a ski boot although my doctor said its fine, but your doctor may have another type made of of some other material that might work