John,
If you’re doing this loop from Manker Flats, you’ll find my GPX file near the bottom of the guide. You can download this and use it with many GPS apps and devices. But then, that doesn’t really answer your question about a map now, does it? 🙂
You used to be able to get USGS topo maps at any decent outdoor retailer, but often they don’t carry them anymore. If you do a lot of hiking, you might want to invest in National Geographic’s TOPO! software (for Mac or PC). This will let you print your own maps and even plan routes. They will try to sell you on special water-resistant paper for printing on, but I print mine on normal paper and then put it in a clear plastic page protector.
If you prefer a large traditional topo map, I recommend (and own many) of the Tom Harrison maps. Here’s the one for Mt. Baldy (officially Mt. San Antonio) and surrounding area.
Thanks for the kind words about the website. Keep coming back and sharing your feedback and trip reports!