Bardic Knack + Jack of All Trades = effectively having half ranks in all skills. The Collector of Stories skill trick gives you a +5 on knowledge checks to identify creatures. There are some items that boost all knowledge skills, but I forget where and what they are now. Obtain Familiar can give you two rolls on all skill checks, since the familiar has your ranks. Knowledge (History) gives a +2 synergy bonus to bardic knowledge, and I know there are a few items hidden away that also add to it.
Other than that, you're going to have to rely on divination magic, I think. Contact Other Plane is crazy powerful, and if you can get a +5 int bonus, you can take 10 on the intelligence check and so never risk failing it. Scrolls should let you use that to divine what your mundane knowledge abilities can't.
Now not going with an Int based caster causes you to lose out a bit on synergy here, but I guess you could make int your prime stat, and cha your secondary.
Oh yeah, you're going to want access to the cleric spells Guidance of the Avatar and Divine Insight. Between those, you can get a +35 to a skill check. The second relies on caster level though, so if you're getting it from a magic item you likely won't get the full bonus (or you'll pay through the nose for it). A cleric cohort is the easiest way to get these, though...
Edit: Or Ur-Priest... yeah, that could work nicely.