[Home Depot, Lowes...its standard plumbing stuff. It will be schedule 80 (gray) not schedule 40, its on the next isle over from the regular PVC in most of them. Just ask where thier barb fittings are.
Instead of trying to drill the hole perfect, and screw the barb into the plastic and glue it up??!! Forget that lol, just go buy 2 PVC coulplings and an O-ring from home depot and you can make your own bulkhead / gasket. I'd use 1" if there is room too, not 3/4 for your train thats pretty tiny.]