Orthotics in NE

i would go to a ski shop that sells custom footbeds, most shops should have them.  they will cost you about 100 bucks though. we have dfp's at the shop here, i live in montana or id help you out.

i just googled it and in Glen, NH. there is this...http://www.bootfitters.com/shops/jackfrost.php

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

There are basically two types of orthotics (footbeds)- accommodative and corrective.  What most any ski shop sells will be accommodative footbeds, ones that work with your specific foot.  Doctors and P.Ts make corrective footbeds, ones that actually change and alter your foot's normal structure.  From what I have seen, about 90% of people who think they have "flat" feet actually have super flexible feet that collapse and become flat.  Everyone's feet are made up of 3 main arches, so to have a totally flat foot is a medical anomaly that would need serious attention.  I always thought I had super flat feet, but as it turns out I just have super flexible feet that collapse under by body weight and the proper accommodative footbed worked wonders for me.

If you are close to Burlington, PM me and we can talk in more detail about your feet and what footbeds might be best for you.