They make bulkeads for PVC pipe, either SLIP (to accept a pipe directly with cement) or threaded, to take a threaded end. I prefer the threaded ones because you can reuse them, and for someone that changes his plumbing more than his underwear, that's a plus.
What size you need depends on the size hole you have. Just measure the diameter with a caliper (or tape measure in a pinch). Then go to any website that sells bulkheads like Aquatic Ecosystems or Marine Depot, etc and figure out what bulkhead fits the size hole you have.