There are quite few people/companies producing gear these days and some are run by people who are members here. A lot of the companies are new but a number have been around for years.
Here's the list from MTBR.com:
Revelate Designs LLC
Anchorage Alaska and Springfield Oregon
Cleaveland Mountaineering
Grand Junction, CO
Custom Bicycle Bags from Porcelain Rocket
Calgary, Alberta
Wildcat Gear
Wales, UK
Phantom Pack Systems
Canada
Bike Pack
Poland
Bed Rock Bags
Colorado
Bike-Bag
UK
Bolder Bikepacking Gear
Boulder, CO
Becker Sewing and Design
Fairbanks, Alaska
J.PAKS_Adventure Cycling Frame Bags
Denver, CO
Barking Bear Bagworks, jsnsnll@gmail.com
Conway, MI
Nuclear Sunrise Stitchworks
El Paso, TX
OVEJA NEGRA threadworks
Salida, CO
Lone Mountain Innovations LLC
Northern Idaho
Alpkit
UK
SpoK Werks
Switzerland
The site is now dead. If it doesn't return, I'll delete the link.
Jandd Frame Packs
San Diego, CA
Bike Bag Dude Custom Frame Bags
Mt Hutton, NSW, Australia
Wanderlust Bikepacking Gear and Fatbike Pogies
Missoula, MT
Rogue Panda Designs
Flagstaff, AZ
Apidura
London, England
Andrew the Maker
Kansas City, Missouri
Stealth Bike Bags
Wellington, New Zealand
RockGeist
Winston-Salem, NC
Switchback Bikebags
Wheat Ridge, CO