You've got a few choices:
-
Casascius.com-Ebay
-BitcoinTalk Goods and Auctions forums
-The Bitcoin
collectible marketplace thread.
With Casascius, you will pay the lowest premium possible...provided you order in large enough quantities. Mike charges a premium for single-coin purchases in order to leave room for resellers in the market.
With Ebay, you will pay the highest premium. They have additional fees, and PayPal chargeback scams are relatively common. If you go this route, do your diligence.
If you've got time on your hands, scanning the Goods and Auctions forums can be a great way to pick up a deal, or find exactly what you're looking for.
The collectible marketplace thread attempts to aggregate the listings in the goods and auctions forum. However, it focuses on those that are of a limited run. So in your case, I'm not sure it would be terribly helpful. It might still be worth visiting to get an idea of the various pieces that are out there. For example, Goat just put up a listing. He used a very nice notation (one I'll likely adopt) to list his offerings. You'll find there are various Series, as indicated by their hologram/window. The material varies - you can buy brass or silver coins (and very rare, gold).
nightowlace has a regular offering of
2013 Brass coins that have been graded (by ANACS). This is a bit of a middleground between a high-end collectible and a basic, brass coin. Going forward, it puts your mind and future buyers' minds at ease by knowing the coin can not have been tampered with. You get a standardized grading so future prospective buyers know the quality they are getting.
With all this said, I think your best bet would be to wait for a Group Buy for 2013 1 BTC Brass Coins. There is not a lower-premium method I am aware of, short of buying 50 from Mike, of obtaining a Casascius coin.
