Amann serabond thread, also known as bonded polyester thread.

Available
Tex-90/V-92
Tex-135/V-138
Tex-210/V-207

At about 1LB spools for all polyester thread.

Great for heavyweight applications:

Leather goods (purses, bags, belts, wallets)
Upholstery (automotive, marine, furniture)
Webbing
Vinyl
Canvas