I inherited a Ruger Standard, manufactured in 1979 from my grandfather. It has one mag, but I'd like to add several more, so I can spend more time shooting than loading, but it appears they no longer make Standard-specific mags. I've been reading several forums and trying to get to the bottom of it, but can anyone with 100% certainly tell me which (if any) Ruger magazines are compatible with this pistol? It's been surprisingly difficult for a noob like me to figure it out. Thanks in advance!