I just got one from CompUSA (CompUSA branded). I probably paid too much ($70), but I didn't have to wait for it to be shipped. There a 3 flavors: 2.5" for laptop drives, 3.5" for hard drives and 3.5"/5.25" combo that will hold a hard drive or a CD/DVD/... Most of the brands are not big names. They run from about $50 US to over $100. Do a search on pricewatch for "USB 3.5 enclosure" and you will get many hits. BTW, almost all support both 1.1 and 2.0. Perhaps someone else could ring in about the different USB chips. Some e-tailers will tell the USB chip, others will not.
Mine works great except that the instructions were wrong. They said to make the drive Master, but it worked when I removed the jumper and made it a Single.