You might check Campmor or Sierra Trading Post. I don't like convertible pants (or long pants) myself; I hike in shorts year around, and layer long johns under them in colder weather. If I need some long pants (a cool evening in camp, or a long stretch of grass heavy with dew, or such) I just use my rain pants.
I finally broke down and bought a pair of Kuhls. I hike so much the cheap light convertibles developed holes in the rear within four months.
And, I stopped buying convertibles, since I never zipped off the legs. The Kuhls I have roll up into cargo capris - walking with them rolled up was a mistake, I ended up with burrs in my socks and too much junk in my shoes.
"In the beginner's mind there are many possibilities. In the expert's mind there are few." Shunryu Suzuki
Loc: Gateway to Columbia Gorge
Because of the extra seams and zippers, a pair of convertibles generally weighs close to the same as a pair of plain pants plus a pair of nylon swim trunks. The advantage of the latter is that if you need to wade, you can go ahead and get them wet yet you still have a pair of dry pants. Or, if the pants get wet, you can wear the swim trunks over your base layer bottoms. (That used to be high fashion for backpackers, and some still do it.) On a recent fishing trip, my grandson kept wading yoo far into the lake, and he was wishing he had swim trunks instead of convertibles!
The ones you'll find at Big 5 or other budget sporting goods stores or at Campmor.com aren't as sturdy as the expensive ones, but they work. I do recommend stitching the crotch seam for reinforcement before you ever wear them. (Don't ask me how I learned this! )
As PDA says, your local thrift stores can be a great source for backpacking cothing. So, for that matter, can your closet! Just be sure they aren't cotton!
Edited by OregonMouse (09/23/1307:35 PM)
May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey