I've been working with one of my sponsors as a professional climber to come out with a more affordable and stylish version of the convertible pant for the all around outdoors person. The details are coming together; the key being the removal of the goofy zipper and inability to awkwardly lose one of the lower legs. Check it out:
They are offered in almost any color imaginable and size, although blue and tan may be the most common and durable options (especially waist size 36-38).
Available at any thrift store for $5-10, or at Urban Outfitters for $75 if you prefer the used look but not the smell.