There are quite a number of suppliers of trews, some of whom make their presence known here.

You might be interested to see that trews may also be made cut on the bias, much like they were in times gone by. I am sorry about the quality of this picture, but it shows the trews belonging to a good friend of mine that recently were made by his tailor. They are bias-cut, in a Stewart tartan. They are extremely fine looking! Maybe JS will send me a better pic.