All packages that includes Czech Republic games were sold out in 5 hours (the one with CZE-CAN was sold out in 20 minutes). I'm not sure if they sold as many as they could or kept a specific number to be put on sale in February, but even in this case you would need to be very lucky to get one. The Sazka tickets website puts you in a queue when you try to login, which keeps the server load acceptable, but you need to be among the lucky ones who get in before it's too late. Packages were put on sale at 8, and when my turn came (at 10.30) CZE-CAN was already sold out (I didn't look at CZE-SWE, but it probably didn't take long to sell out). I still could get tickets for CZE-FRA.
If you're want to see the 2nd game of the package, I guess that many people were only interested in the Czech game and will be selling the other ticket, so if you show up at the arena one hour before game time you should be able to get one.