I don't know which you have and don't have but here's a few that Im sure a lot don't have
Theres a ton of vendor ones as well, all throughout Outland/Northrend - hopefully you have those
http://www.wowhead.com/item=20769 - takes awhile to farm but not terribad
http://www.wowhead.com/item=8494/parrot-cage-hyacinth-macaw - rare usually up for about 15k on my server
All 10 of the faction tourney pets
http://www.wowhead.com/item=64494/tiny-shale-spider - have to get a lot of help for this one
http://www.wowhead.com/item=64403 - seems like it would be really hard to get but possible
http://www.wowhead.com/item=43698 - long time but farmable
http://www.wowhead.com/item=44738 - just lots of standing in Dal - don't know if you can get at 19 but you probably can
All the whelplings - Crimson, Azure, Emerald and Dark
The crated pets - Enchanting (Enchanted Lantern, Magic Lamp) Engineering (Lil' Smokey, Pet bombling, umm de-weaponized mechanical companion, the World Destroyer, Mechanical squirrel, lifelike toad, mechanical yeti)
Darkmoon faire- has the frog vendors and Jubling quest
Theres also all the faction vendor pets - like snakes from Org and Dragonhawks from Silvermoon and Owls from Darn and Kittens from SW
Black Tabby Cat - don't know if this is still obtainable after the shattering
Hope this helps, I know its not your exact specifications but I don't know you at all so Im not going t to make an extensive guide on pets for 19s
Helpful Sites
http://www.wowhead.com/items=15.2#0+1
http://warcraftpets.com/wow.pets/index.asp