You can try Zone 9 Tropicals, Grassy Knolls Exotic Plants, Caldwell Nursery or Kartuz.
Karyn

Looks like Karyn covered it..Unless you want to start it from seed.. They are one of the easier/quicker ones I think.. ebay has seed.. Good Luck on your search...
Chena

You can buy 3gallon passionfruit plants(Purple Possum/ Brizilian Golden) at Pine Island Nursury for excellent prices($25 or $35) They said they'd be offering quadrangularis in about 2 months. You can also go to White Dove Passionfruit Farms(ebay)to get cuttings.(20 frederick for about $39)