A few on ebay from America. Gonna purchase some for myself because they would make my life so much better than trying to wedge a baby food jar lid in between the branches of my wood. The amount of times they have slipped out of my hand and spilled over the substrate would surprise you!
Small - Zoo Med Mushroom Ledge Small For reptiles and amphibians terrarium | eBay
Large - Zoo Med Mushroom Ledge (Large Size) | eBay