Steve's suggestion, don't be shy. Call out clearly what you want. The volunteer that has it should respond and hold it out. The volunteers want to get you what you need, and want to help you.
A serious observation: I saw several people come through that looked overwhelmed and undertrained for the event. An Ironman is a BIG event. I encourage all triathletes that want to reach for an Ironman to do it, but please, take the preperation seriously. You don't have to be super lean (but leaner helps) you don't have to be fast, but you can't be slow at all three sports, and you have 17 hours. In my humble opinion you should think you can honestly do it in 15.5 before signing up. This gives you 1.5 hours for "bad stuff" to happen and you will still make it.