An adapter for a canister filling system includes a body having an opening that is shaped to enable insertion of a valve of a gas canister for holding a pressurized or liquefied gas, into an interior space of the body, leaving a sealed gap between at least a portion of a lateral aspect of the valve and an internal surface of the body facing the interior space; and at least one channel that is configured to conduct pressurized or liquified gas from a canister filling system into the sealed gap in the interior space, so as to reach one or more lateral exterior ports of the valve of the gas canister that open laterally to a longitudinal axis of a body of the gas canister, when the valve is inserted in the interior space, to facilitate filling of the gas canister with the pressurized or liquified gas through said one or more lateral exterior ports of the gas canister.