Inconel hyperdermic needle stock. At that location on a turbine, it has to be inconel - stainless will also crap out after a while. I don't know where they source the tubes from (medical supply?), but that's what they use on the fuel ring of turbines. You just need to size it up from there.... By the way, you can get drill bits that small, but they're expensive and I can't imagine how they'd do in a high alloy material.

Good luck - can't wait to see the finished product!