Cabelas Trail Pants, even waist sizes to 50 inches, free hemming:

http://tinyurl.com/5dv45r

Cabelas Trailhiker pants, to size 52, free hemming:

http://tinyurl.com/5mgq2e

in either case I'd be tempted to order them umhemmed and take the pants to a local tailor for hemming.

I know these aren't zip offs, but I hope this helps. Happy trails.
_________________________
--Ken B