Pop into any Restaurant and they will sell you a full gas bottle. Don't pay more than €30 for bottle and gas. Make sure you have an adaptor or connection for the Spanish bottle.
I use my German gas connection, I have an extra German connection, I then cut of the end that will be going into the Spanish bottle, bought the adaptor from a Fereteria (Ironmonger and General store) fixed it into the end I cut off and there you have it. I run my German bottle on one line and my Spanish on another line. I carry a spare German bottle, just before I leave Spain I get a refill on the Spanish bottle. ☺☺