Speaking of small quantities, how about small pieces of Kenyon K+ Tape. As a promotion, maybe stencil or stamp the NEW LOGO on them. It could be safety reflective ink.
As opposed to the backcountry.com or steepandcheap stickers that they throw in their mailings, useful and visible on the trail.
Howabout ultralight velcro, e.g. for quilts.
Most of all, a fabric treatment that repels water and does not compromise breathability or add much weight! A couple of the items in the Outdoor Retailer review look real promising. Is this not the wholly grail?
A quite common request is foam for backpack harness, shoulder and hip. Maybe some prelaminated dual density.
The mesh used on Golite Ion is really cool on the shoulders.
An affordable home model of (ultrasonic?) seam welder. heh.
Various elastic and elastic fabrics for cuffs etc. Tends to be smaller pieces that you need.
Ankle-sprain-proof ultralight trail runners. With built-in air casts or something that you pump up like Nike.
Buckypaper. It’s real