You can also check with lots of Mini owners at "Perfectunion.com"
Look under Mini 14s and at the top should be a fixed forum about mags.
They have many threads about the notoriously shaky aftermarket products, and are worse for the 30s.
The one which appears best is the ten-round metal mag by Promag, in stark contrast to 30-rounders by Promag.
Others swear by PMI, but these are not produced now, from what I remember.
Good luck.
By the way, Ruger is now selling higher-cap. (20-round?) magazines from the factory for Mini 14s for about $35! Read this on that website yesterday. They will probably sell out very fast.
People believe that their motivation for this totally unexpected event is fear of another AWB including detachable magazines.
Ruger never produced any higher-cap mags for anybody except LEOs in the past, for the 14s or 30s.