Woot offers KIAYACI Glass Chair Mat for $71.39 (reg. $260.90) free shipping with Prime. 

Product Description:
KIAYACI Glass Chair Mat for Carpet or Hard Floor Tempered Glass Glass Table Top Table Mat Square 46''x53'', 1/5 inch Thick, Transparent, Clear, A-GE10004-T-46x53x1/5-USAM008