That shop is probably your best bet, the top of la Rambla but there seems to be very few in and around barcelona dedicated golf shops, and the stuff is the same price if not dearer than here its a very designer city these days. America is the place to go for it
You could always try a trip to La Rocca Villages.... it's an outlet shopping place about an hours bus journey outside Barcelona. They definitely had a few golf shops when I was last there and good value for money