Got to a pedorthist, they usually have a good selection and you can find one that fits your foot.

I've used Kneed2ski, and if there's enough room (there usually is) I prefer the thicker Kneed2move.  I've got moderately high arches.

Posted by: @steven-cao

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Anyone have an insert they like in their snowboard boot.  My arch gets sore if I get my boots too tight or I've been riding all day.

I have high arched feet, higher than any off the shelf orthotic I could find. Used a cheap but firm based insole, cellophane food wrap, and acrylic curing bathroom sealant to mould my own supports. YouTube for the details below. Results were very successful and have lasted 30 days plus riding. Cheap, effective and easily repeatable.