Where is the best place to buy a large cylinder for this? I have https://www.amazon.com/gp/product/B00CA31IMY/ref=ox_sc_sfl_title_17?ie=UTF8&psc=1&smid=A2GC75WQEN3ZW2 and https://www.amazon.com/gp/product/B00D8M5NZY/ref=ox_sc_sfl_title_18?ie=UTF8&psc=1&smid=A22I86T3E2LCX5 in my cart for this tek.