I’ve sold my SPS-500 but still have a SOtM Silver Y DC cable (5.5mm x 2.1mm) for sale.
List is $660. Offering at $330 with free shipping within CONUS.
Item link at SOtM: https://www.sotm-audio.com/sotmwp/english/shop/dc-cable-for-sps-500/
Customer service is extremely important to me. Please see my stellar feedback at Audiogon (davidfyoung), eBay (davidfyoung), and USAudioMart (dfyoung).