Ryobi is a generally well regarded brand when it comes to all sorts of power tools. Therefore if you are looking for an electric line trimmer the Ryobi RLT4027 Electric Grass Trimmer must surely be worth consideration.
The Ryobi RLT4027 is widely available. The cheapest seller I can find at the time of writing this is Tooled-up.com, other retailers offering it at a competitive price are Very and Robert Dyas.