I bought my sorbothane 50 durometer half-spheres (two 30mm and two 40mm needed per printer) rom the seller "soundupgrade" on eBay: https://www.ebay.com/itm/SORBOTHANE-ANTI-VIBRATION-FEET-11-19-25-30-40-50mm-Turntables-Speakers-PCs/290971718688