James Burleigh
Furniture (Contract/Commercial)
Flexiform Business Furniture
Orangebox
Gresham Office Furniture
S•CAB
Pretty outdoor furniture and lightweight metal interior and work furniture
Fenabel
Perfix
lockers, filing, towers and storage cabinets
Ghidini 1961 | Contemporary Italian Furniture
MaxAlto
Metadil Store
Southwest Solutions
Cider
Halle+
Industry West
Blu Dot
Not sure if this is contract grade furniture, but I signed up for a trade account and 3D files and spec sheets are available.
COR
I've used many of their lounge seats, including "Shrimp" and Nenou. They provide downloads here: https://www.cor.de/en/downloads (and on BIMObjects)
Egan
EMU
BuzziSpace
Götessons
Most of their revit downloads are on BIMObjects.
Glimakra
Really cute stuff - acoustic hut pod (nice revit file), poufy beanbag chair, tree-like dividers, leaf acoustic hangings, accessories.
DVO S.R.L.
Zeitraum Sustainable Furniture
WOUD - International
Wewood
Wendelbo
Vitra
Verywood
Varaschin
True Design