Here are some of the symbols that seem in some fashion associated with "the Priory"...
 

Le Cercle Dagobert II "Alpha and Omega"	Le Cercle Dagobert II "Seal of Dagobert"	Saint Sulpice "Auspice Maria" (?)
Alpha Galates "Cross of the South"	Priory of Sion Logo (1956 Statutes)	A.O.M.P.S. logo (origin unknown)
"Sauniere Bookplate" (not really his)	Sauniere Church design above altar	Le Serpent Rouge Seal

 

 Observe a few things:

• The similarity between Le Cercle Dagobert's symbol and that of the Sulpicians. If that is supposed to be an A in the Sulpice logo, it's missing a bar.
• The similarity between the top and bottom of the Alpha Galates/PoS logo (both are "Aquarius" ?)
• A symbol from Sauniere's church also appears on Le Serpent Rouge.