Originally Posted by Azrayne

First thing to ask yourself is whether you have a shadow priest/moonkin available the majority of the time? I imagine most 25 man guilds, and no small number of 10 man guilds, would, in which case you can drop back down to 289 hit.

As far as specific items go, Mark of the War Prisoner from H VH and Dying Curse from Naxx25 both provide a large chunk of hit rating and a nice DPS bonus (73 hit and a SP useable, and 71 hit and a SP proc, respectively). Can't go wrong with either of them, especially since your trinket choice at the moment is decidedly lacking. Grab whichever one you can get your hands on first, throw a belt buckle on your belt and gem it with a SP/hit gem, bam you're capped, have fun.

If you want to be capped out assuming no moonkin/SP, you're going to have to do a bit more thorough of a regearing. But that's not too big a deal, considering you're still wearing a large number of level 70 items which presumeably you're going to want to replace at the first available opportunity anyway.

I posted a gear setup in the 'best non-raid mage gear' thread which will cap you out at 14% hit and give you very respectable stats without requiring any raid loot, and there's a load of other good suggestions for gear there as well: Best Non-Raid Mage Gear