Legitimate Sources of Relics, how Churches and Priests May Request Them

Legitimate Sources of Relics

Parish Churches and priests who wish to obtain first class relics for public veneration may apply to the Vicariate in Rome. A vast store of relics is preserved there for this purpose. They will need to provide proof of status, and may ask the requestor for a letter from their Bishop to approve the request. The Vicariate no longer distributes relics for private veneration in order to avoid abuses.
 
Some religious orders and jurisdictions provide first class relics for private veneration.
 For example the Mother Seton Shrine in Baltimore distributes first class relics of St. Elizabeth Ann Seton. 
The Eparchy of St. Maron of Brooklyn sometimes has first class relics of Blessed Rafka and Blessed Al-Hardini. 
In addition, if one goes on pilgrimage to any shrine, it is worth asking in the official gift shop or sacristy as relics are sometimes available from these sources.

Relic cards and medals with second or third class relics are available in Catholic bookstores or from religious orders. If there is any particular saint you're interested in, look up the address of the provincial postulator of their order in your local Catholic directory and write and ask. 

In addition, you can make your own third class relics if you visit a saintís tomb just by touching the tomb with a piece of cloth. This method is sanctioned by a very ancient tradition - there are records of pilgrims to St. Peterís tomb doing just this in the 5th century.