Might be best to buy them off eBay since they have no digital value attached to them any more, found these from a quick search:
2011 Series 2 Casascius -1BTC Coin - $425
Casascius 5 btc physical coin - $55
1x 1 BTC Casascius Physical Brass BIT COIN 2012 - $135
2012 Casascius Coin (Bit coin) - Redeemed / No Bit coin - $95
2013 Casascius Coin (Bit coin) - Redeemed / No Bit coin Value/ Physical Bit coin - $115
Ebay prices are pretty insane. I would hazard to guess that many buyers are that dumb they still think they're getting a bitcoin to spend despite large letters in the ads.
You'd get a better deal if you could find one on here. Everyone's more clued up. I've seen prices of around 0.1 BTC for redeemed brass coins.