Amazon has the Glorious Gaming 57g Ultralight Model O 2 PRO Ambidextrous Wireless Gaming Mouse (GLO-MS-POWV2-1K-B) for $34.99 with free shipping on $35+ or with Prime. 

Also available in 60g Ergonomic (GLO-MS-PDWV2-1K-B) for $35, while the 59g  4K/8K Ambidextrous (GLO-MS-POWV2-4K8K-B) version goes for $45.