You have to "load" or send any desired amount of bitcoins to the address found on the cheque, then it becomes a physical bitcoin note.
I'm not sure how to buy some with cash, but maybe you can ask Senbonzakura to give you a redeem code for one for free.
You can check with cheque producer if there's a way to buy them as cash in mail on his website or on the forum.
You can pay in bitcoin with some sort of cash through options on BitInstant if you're in US, Russia or Brasil, or send cash through a bank to exchange and get  a redeemable exchange codes from BitStamp or MtGox, if you're in some other country (Ireland? Greets from Croatia!).

Or

You can print your own bitcoin note such as this one for the same effect of having a paper bitcoin note, if you do not need security properties such as peelable sticker hologram on a cheque.