CDNN has a straight 20 round mag for Mini-14, looks like an M-14 mag rather than the normal curved 20 round mags. They say it is made by the same manufacturer who makes original equipment Ruger brand mags. They're $15, about half of a Ruger brand one.
It got good reviews on another site that has a good reputation on Mini-14 matters, Perfect Union https://www.perfectunion.com/vb/ruger-mini-14-mini-30/
They also have 10 round mags by the same company for half the price of Ruger brand.
I've read they don't stay in stock long, seems like limited runs, so I ordered two of each size.
If anyone is interested, here's the link for the 20 rounders: https://www.cdnnsports.com/mini-14-223-20rd-premium.html#.XZoXiyUkrVo
It got good reviews on another site that has a good reputation on Mini-14 matters, Perfect Union https://www.perfectunion.com/vb/ruger-mini-14-mini-30/
They also have 10 round mags by the same company for half the price of Ruger brand.
I've read they don't stay in stock long, seems like limited runs, so I ordered two of each size.
If anyone is interested, here's the link for the 20 rounders: https://www.cdnnsports.com/mini-14-223-20rd-premium.html#.XZoXiyUkrVo