There are a more than a few ways you can find a marriage record around 1903.
1. East Carroll Parish Courthouse -
Go to the courthouse and the staff will direct you where the marriage records are. Each book has an index that is included in the very back that is by groom and sometimes by bride. You will get to handle and view the original record, but you cannot make copies of it.
2. Order microfilm from your local Family History Center -
Marriage records for the parish were microfilmed during the mid sixties by the Mormon Church. You can order FHL US/CAN Film 311910 which are marriage records in volume G, years 1898-1906. The index is included in this roll. The cost to order the film runs at about $6-$7 and can be ordered online (depends on where you live) To find your local center, please visit https://www.familysearch.org/locations
You can make copies of the microfilm copy at your local FHC, and some offer digital scanned copies that you can save on a flash drive or CD.
Additionally, you can visit the Family History Library in Salt Lake City or the New Orleans Public Library's Main Branch (downtown) to find a marriage record for that date. Both of these facilities have microfilm copies of the actual record in the courthouse.