Canon EF 70-200mm f4 IS USM L
You want a medium telephoto lens for your Canon dSLR, something with a constant aperture, solidly built with pro quality, yet light enough to carry on adventure to some faraway part of the world. You have looked at the f2.8 models but didn't think you could afford them or the Sherpa to carry them.
Professional grade build quality, including dust and moisture sealing; four stops of image stabilization system; relatively lightweight
The tripod collar is optional; relatively expensive