10 round magazine for Thompson Center

Where can I find a 10 round magazine for a Thompson Center Classic .22 rifle. A local gun dealer has had a couple, but can't find any now. I emailed the factory, and they said they would not be available till summer. When I bought the rifle, the factory was 3 months backordered for 5 round mags. I was able to buy them from Midway, but they don't list the 10 round mag.