Frontline Gaming (I like these guys)

https://store.frontlinegaming.org/gaming-mats/

(comes on a mousepad material with zipper storage bags; very nice! I have several from them)

Urban Matz (has a big logo on their mats if I remember correctly)

https://www.urbanmatz.com/

Gamer Matz

http://www.gamematz.com/grass-field-tabletop-war-gaming-mat/

Mats by Mars

36" x 36" Game Mats

Cigar Box Mats

http://cigarboxbattlestore.bigcartel.com/

Deep Cut Studios

http://www.deepcutstudio.com/