What sort of buff have you got in mind? I've got Bull's strength, Bear's endurance, etc... enlarge creature, haste, magic weapon, keen edge (the last two, granted, not so useful on your bear form) Animal Growth (much better for use on animals, I don't know if it applies to your transformed form, though)
--edit--
unrelated, I note that the Telekinesis spell does not list what size modifiers are used for combat maneuvers or what weapon size one is considered to be wielding for disarm attempts- I would assume it defaults to the caster's size and being treated as unarmed.
It is based upon
Polymorph, so my type changes to animal. How do you have
Animal Growth? Oh, wow, it is on the Sorcerer/Wizard list. +8 strength, +4 con, +4 to saves, that looks almost useful... Where is enlarge creature from?
At the moment I turn into a
Black Bear as per the
Polymorph spell except that I get the physical stats as bonuses(+8 strength, +2 dex, and +4 con) instead of absolutes(19,13,15). Although I don't use it much, I only get 2 a day and I lose some of my gear, most significantly my two-handed weapon and its lovely power attack. I am pretty sure that haste would give me an extra claw attack though, so that ought to be handy. I could probably get a full attack sequence using unarmed strikes, but that seems a bit silly... Once I start taking Warshaper in two levels time I should have all the cheese I will ever need...
P.S.
I am just discussing this stuff as an academic exercise and to keep you informed. Please do not feel for a moment that I would want you to compromise your character in any way just to gain a buff or two.