I am not able to recommend a particular podiatrist but most of the Orthopaedic supply shops offer an orthotic service - they are generally found near a hospital and usually have a window display of crutches, wheelchairs etc. Have a look in the yellow pages ~
PagineGialle.it ~ for the one nearest to you - they are listed under " Ortopedia - Articoli" .
Although I have never used them I do know T&F who have branches in Macerata and Appignano definitely offer a custom made service - they have all the computerised pressure plates and use the foam block system to form the cast.