Control valves for propane gas can be found online at Amazon from a number of manufacturers, as of 2015. Adaptors, pressure regulators and other propane gas accessories are also available through Amazon.
A Nashfuel Propane Tank Service Valve is available through Amazon for $21, including free shipping, while a Hot Max Brass Replacement Needle Valve sells for $9.22, with additional charges for shipping, as of 2015.
Needle valves from manufacturers such as Parker, Industrial Grade, King Kooker and Trerice can also be found at Amazon under a search for propane valves.
Amazon offers free shipping on orders over $35, as of 2015.