For the best detail of the trail, you'll want two USGS 7.5-minute quads: Mt. Whitney and Mt. Langley. Those cover everything from Portal to summit.
You can order them direct from the USGS out of Denver by calling (303) 202-4700, or you can call any of several topo map dealers, like Map Express at (800) 627-0039. You'll pay a premium over the $6 per map if you go to a dealer instead of the USGS, but you generally get faster service from the dealer, if you're in a hurry.
The <a href="http://www.topozone.com">topozone</a> alternative is good, especially if you have access to a large-format color printer. You can print out just what you need and tape it together for the trip. Cheaper and faster, but the ink will run if it gets wet. (Unless you're lucky enough to have access to a large-format color laser printer!)