You can't tame the pre-searing bears anymore. You used to be able to do so with a certain build and with help. However, the devs fixed it so that you can't tame them anymore.
The pets you can tame pre-searing are:
Striders (birds) - all over the place
Warthog - just outside Ascalon City & in the Northlands
Wolf - Ascalon fields (outside the abbey)
Melandru's Stalker - Regeants Valley by the shrine/statue of Melandru (you need to tame one of these for the ranger quest..)
I believe thats all the pets ytou can get pre-searing..
Post-Searing you can also get:
Dune Lizard (Fern Lizard?)
Black Bear (Lorner's Pass iirc)
Warthogs (Maguuma jungle region)
Lynx (Krytan region)
Snow Wolf (Shiverpeaks)
Melandru's Stalker
Moa Bird (bloody chickens!

)
Hmm.. think thats all..
Edit - If your unhappy with a pet, you need to talk to the guy just ouside of Ascalon. He's got a title of tamer or something like that (sorry, can't remember the name right now). He's the same guy who was standing close to Master Ranger Nemtre (sp?) in Regent's Valley pre-searing. Talk to him and he will take the pet off your hands, but once you do this your pet will be gone forever.