Hey Gil. Not sure about the RO Jet specifically, but Lowes and Home Depot carry a variety of O-rings in various sizes in their plumbing departments. We also use regular nickle plated copper wire twisted tight securing/clamping our pantyhose material stretched over the venturi, as well as cable ty-wraps pulled tightly. Also, auto parts houses sells the green o-rings used for auto AC systems...many sizes to choose from. They hold up pretty well to heat, as auto AC sys can generate some serious heat.