MapSource is Garmin's proprietary uploading software. I got my GPSr used and got the software off Garmin's website. I was lucky When I bought mine, the seller had everything for it-book, extra card, cable and some maps. I downloaded the software and then a map from gpsfiledepot. Then I was able, as JPS mentions, to create a map of just the sections I wanted and load that onto my SD card. It took me a while to figure out how to do it, but the tutorials jps linked to in his post are pretty easy to follow.

My particular GPSr is bigger than most, not sure why, and the screen is smaller than the newer Garmins, but it runs on AA batteries, which I like, and I got it at a great price, so no complaints. It will run on rechargeables, so I imagine the 60CSx will too. I have a kit from Eneloop (Sanyo) that I think came from Costco and haven't bought batteries in years, except a few as backups for winter travel.