The most common and affordable way to start a Mark Buehrle collection would be with his rookie cards, which come from products released in 2000. He has five in all, including one jersey card and one numbered to 999 - still a huge print run by today's standards. In fact all of his RCs were produced in quantities big enough that a great performance, even a historic one like a perfect game, won't move the needle on them too far.
Even after his perfect game, the cards can easily be found for below book value, with one (his Fleer Tradition Update #U17) sometimes changing hands for under a buck. Buehrle's Bowman Draft #69 and Bowman Chrome Draft #69 are probably his most popular, but both are easy to find.
If a Buehrle autograph is the target, those can be found on cards too. The Beckett database has 161 different autographed issues for the pitcher so far, which sounds like a lot but really isn't for a guy who's wrapping up his tenth year in the majors.
Other items with Buehrle's signature can also be found online, including baseballs and photos commemorating his previous no-hitter in 2007. Steiner Sports offers balls and pictures with inscriptions from that game starting at $199.99, but some hunting on SportsBuy or eBay can turn up similar items with the Steiner C.O.A for as low as $79.99. Expect an offering of items celebrating the perfect game to pop up in the not too distant future.
For the "money is no object" crowd, there are some interesting auctions currently running on eBay with some more limited collectibles up for grabs. One seller is offering the red ink variation of Buehrle's 2001 Topps Heritage autographed card (limited to 52 copies) for just under $600. Another is asking for $1400 for a game-worn jersey from the 2007 season.
Finally, the most ambitious lot brings together three items from the perfect game itself: a ticket, a scorecard and a foul ball caught during the second inning of the game. With just under two days to go at the time of this article, no one had taken a stab at the $10,000 starting bid, but the fact that 268 people had checked it out says that Buehrle is definitely on the minds of collectors.