Are chef's pants like medical scrubs? If so, it looks like there are Unisex patterns available in McCalls, Simplicity, Kwik-Sew, and New Look. Generally, I have more fitting success with Kwik-Sew patterns, which you can buy at Hancocks or order from online sources.
Quilting cottons make great scrub tops, but wouldn't they be too light weight for pants? A poly/cotton twill would wrinkle less and would be heavier in weight--- more like a chef's jacket.
You might do a "quick and dirty" test pair of pants, whatever pattern you choose. Pants take a bit of fitting to get the length and crotch seam fitting correctly. You may also find that you don't save much money since pants take a good bit of fabric, but can be well worth the effort to get a good fit.
patternreview.com would be a great resource to do a search for member reviews on scrub patterns and to read up on pattern alterations.