New 20 ounce tumblers available now! Forum donation credit with purchase. https://www.wildguzzi.com/Products/products.htm#Tumbler
Bought mine on amazon. Comes with extension that has a little give built in for tight cornershttps://www.amazon.com/gp/product/B0039LB8PI/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1