High Quality "Wheely Walkers"

My mother needs a new wheelie walker. She has a basic three-wheeled one (I personally consider the three wheel ones to be totally unstable and almost dangerous) and did not like the four-wheeled one that I bought her a few years ago.

It seems to me that most of these walkers that are sold by disability shops are really cheap and cheerful (even cheap and nasty…) models. I would like to buy her one that will be more comfortable to use, have decent brakes and not just those metal things that lock the wheels and even pneumatic tyres. Her current one rattles and causes her hands pain.

Does anyone know of any places that you can go to (either in person or on the Internet) where much better quality walkers are sold? An example of something that looks so much better are the models made by Trionic in Sweden.