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Amazon has BalanceFrom Puzzle Exercise Mat with EVA Foam Interlocking Tiles (Six 24x24x0.5" Tiles, Black, Covers 24 Square Feet) for $ 15.19 after you clip the $ 1.25 coupon. This is highly rated product (over 4 stars and 752 customer reviews) and includes the edging as well.
Shipping is free for prime members or if you spend over $ 25.