Depends.
Yes, if you are wearing them for a medical reason.
No, if you are wearing them for a "don't fit in stocked & standard boot size" reason (which your Unit could just call Clothing Stores/Unit QM to verify is actually your case).
If you just want to buy them on your own and wear them "just because" --- then you should consult with your RSM before expending the bucks to find out whether or not your Unit policy will allow you to wear your own purchased footwear.