So here's what I got done last night. I removed the steel bar end weights that were in the stock drag bar. I made a channel along each one for the wire to run through. I had previously drilled and tapped the ends to accept 5/16" bolts to hold the mirrors on. That works MUCH better than using the expanding aluminum sleeves that come with internally mounted bar end mirrors.

I drilled and tapped a 1/4" hole into the weights. I did this while the weights were positioned inside the handlebar so that both the handlebar and weights have lined up, matching screw threads.

I ran a 1/4" headless set screw through the bars and into the weights. I screwed them in til they were flush so as not to interfere with the grip/throttle sleeve. You can see the channel for the wires.

I thought about welding the weights in the bar, similar to the stock drag bar method, but decided to go with the headless screws so I could remove the weights if needed.
Next, I took a washer and made an opening in it for the wire. I used JB Weld to attach it to the bar end weights. The washer acts as a spacer for the wire.

Here I put pressure on the new wire spacer while the JB Weld cures. You can see the space for the wire.

Here you can see where the wire exits the bottom of the bar. I took this pic when I first started running the wires. I'll run the wires through the existing wiring covers for a nice, clean look.

The wire has protective heat shrink tubing throughout the section that runs through the bars. I also rounded all metal edges that the wire comes in contact with. I thought about doing the hollow threaded rod in place of the bolt but the solid bolt is stronger and gives me more flexibility for attaching things to the bar ends.