Looking on Amazon, there are lots of offers, but most appear to be the same manufacturer, ATC. More important is the range that it displays, most beers that I make start with a wort S.G. between 1.040 and 1.070, but if you plan to make a very strong beer or wine, its useful if it goes up to 1.100 or slightly higher. Several are listed as 0 - 32 Brix, which is equivalent to 1.000 - 1.120, which is probably ideal. There is a simple calculation to convert between Brix and S.G., but if you can find one that has a dual scale, that saves some hastle.
You may also consider looking on ebay, I bought one from there last year for less than a fiver and it works fine, far more convenient than using a hydrometer. Just remember that it should only be used to measure original gravity, as the presence of alcohol in the liquid will cause an inaccurate measurement.
