Costco (in Canada at least) has these sweet rubber mats that remind me of the gym. Way cheaper than Amazon since they are heavy as heck! It's flat on the other side :
Amazon.com : IncStores 4'x6' Premium Mat - Vulcanized Rubber Exercise Mat, High Density Floor Mats for Gym Flooring, Home Gym, and Horse Stall Mat (Black, 3/4" Thick - 1 Mat) : Sports & Outdoors
Roll of Rubber Flooring Gym Mat - Bells Of Steel Canada
Rubber Gym Flooring Canada | Gym Floor Mats and Tiles
Rubber Garage Flooring Buying Guide
Fitness | Rubber Flooring | Perfect Surfaces
Technoflex Technofloor 48-inch x 72-inch (3mm) Black All Purpose Reversible Rubber Mat | The Home Depot Canada