You can try these from Amazon. I’ve been buying the same ones but sizes for Riot V2 on my Wave and they’ve been great. I’ve linked below the one sizes for the atlas.

D&D PowerDrive 340-5M-09 Synchronous Timing Belt, Rubber, (Pack of 1) https://www.amazon.com/dp/B00ISCF74Q/ref=cm_sw_r_cp_api_i_FEZ776E7J8E4X2CCRP2R