Well... it somewhat depends on the source, but the Gauntlets of Ghost Fighting are a cheap way to beat the miss chance from incorporealness (and they also work for spells...). IIRC there was a weapon ability called Blood Seeking that also helped, but that might only work against cover (not concealment). Edit: Seeking is the one that basically negates all miss chances, not Blood Seeking.
Yeah, pretty much the problem is that Seeking needs a caster level of 12 and spells that don't exist in E6, and Improved Precise Shot requires BAB of +11. Gauntlets of Ghost Fighting also has a caster level requirement of 13 to create. Blood Seeking requires a caster level of 9th, and in any event explicitly does not function against concealment, so it wouldn't be of much help.
So far the only thing I can come up with that might be of any help is the Bracers of Accuracy in the MIC (duplicates the effect of Improved Precise Shot for spending 2 of 3 charges per day), and the Blindsighted weapon property from the same book. (Grants Blindsight out to 30 feet for 1 minute, 3 times per day. That can be used to ignore most concealment, right?)
I'm just trying to make sure I didn't miss anything