Available from which original manufacturer?? The original " Ruby, which was a copy of a Star made firearm " was manufactured by Gabilondo, AKA Llama, which used a 9 cartridge magazine. After WWI, the guns manufactured by the sub-contracts would be more correctly called Eibar guns, but unfortunately folks like to call all of them Ruby's.
During the WWI era all the Ruby contract pistols were supposed to conform to the same set of engineering drawings. However it was impossible to maintain any type of quality control over so many mom and pop sub-contractors, as a result the magazines often would not work , even between guns made by the same contractor. The French Army made the contractors number the magazines to each gun. Now, warp speed to the present era, magazines offered by the various parts supplies are generic type magazines, designed to more or less work in most of the Browning type Eibar guns. The result is that some of the magazines will work in some of the guns, in others, they will be too loose, too tight or fail to feed. Nature of the Beast. If you order a magazine for a Eibar type gun and it fits and works, go immediately out and buy a lottery ticket
Heck, parts will not even interchange between two like guns from the same maker without file work. JMHO and I have others
PS: As far as I know there are no original manufactures of hand guns left in Spain, Star, LLama and Astra are no long among the living. I believe one or two of the names were shiped to South America but they are no longer " the original " of anything.