Difficult. Try a car boot sale or see if there is anyone on here that wants to sell their's. Whichever, you won't get a gas bottle without paying some sort of fee. I don't remember them being expensive when I got mine. The Repsol petrol station on the motorway into Mazzaron was the one to go to as the one in Mazzaron itself was not keen to deal with non Spanish for the contract.
Jon Faulkner