For the sake of some completeness, Warblade Staffs from DSP Psionics allow you to channel any Touch Attacks through the weapon. It is also treated as a Enchant-able Deep Crystal Bastard Sword with automatic proficiency for the wielder. All it costs is 16,000gp (or 20,000 gp for a greater one with a aoe energy blast option) and Psicrystal Affinity, and of course being psionic.
Of course this is Pathfinder Content, and even 3rd party PF content (though many would treat Dreamscarred Press as equal to the rest of PF regardless), so I dont think you will get much use out of it
Another PF Item is the Conductive Weapon +1 enhancement. Cant Channel Spells, but it can channel spell-like and supernatural melee/ranged touch attacks once per round which if a fairly unique option and opens up a lot of options, definitely something to make a build around, though you have to spend 2 uses of said channeled ability, not all that bad for something like a Warlock though.