I've been combing the internet and found these at Amazon in packs of 3 @ $13.33 each. They work great and are stackable.
https://www.amazon.com/dp/B0CH3JBNH8?_encoding=UTF8&psc=1&ref_=cm_sw_r_cp_ud_dp_R6TX1BDG7RD18VXWHXM3
https://www.amazon.com/dp/B0CH3JBNH8?_encoding=UTF8&psc=1&ref_=cm_sw_r_cp_ud_dp_R6TX1BDG7RD18VXWHXM3