I've seen a couple of different ways that people have found to get a wire from the helmet to the rf; drilling with a long bit, dremeling, etc.
For some reason this particular approach stuck in my head and I just had to try it, whether or not I actually needed a hollow stalk or not.
This is what I did:
I found some brass square tubing that was just the right width for a stalk. Next, I cut a stalk out of wood using a jig saw, then cut away space for the tubing and glued it in place using two part epoxy. viola. 'Just about the biggest hole you can have in a hollow stalk. A little bit of bondo was used to smooth the whole thing out followed by some sanding and silver paint. As for attaching the rf, I had a slightly smaller brass tube (still the square kind) that fit snugly inside of the one in the stalk. I drilled a hole in the rf and glued the tube in place. Everything fits tightly and I can actually take the rf on and off of the stalk as needed. I'll build a more esb screen acurate stalk (with esb tapering) down the road so the fact that I don't have to glue the rf on right now is handy.
Here are some pics (sorry about the quality) that show how it came together. The bucket in one of the pics is my in progress ESB.