I'd recommend contacting a member of the Petroleum Equipment Institute (PEI) in your area. Some may not want to mess with vintage equipment, but there should be a PEI member in your region that would be willing to help, especially one with Tokheim experience.
Here is a link to a search form to find PEI companies in your state. Just select your state from the drop-down menu, leave the other fields blank and click "Search."
http://www.pei.org/search/advanced.asp You can also contact Byron Benford at Ark Petroleum. Byron is a member of Oldgas.com Shop Talk who is experienced with service and parts for operational gas pumps, new and vintage.
http://www.benfordfueling.com/ A bunch of exterior parts are reproduced for the National (Tokheim) A62. Click on "Parts" at the very top line of this page to see some vendors.
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Jim "Oldgas" PottsYour host and moderator