There isn’t one definitive place but here are a few ideas on where to buy sports memorabilia that’s authentic and will add both value and quality to your collection.
Sports collectibles encompass many different arenas (sorry for the pun). The good news is that it's easy to find. Some collectors prefer a mix of different types of items while others stick to one general area of collectibles.
Sports Trading Cards
There are trading cards dating back to the 19th century. Whether you love to collect tobacco cards that are a century old or more, early bubble gum cards from the 1930s, Topps and Bowman cards from the “golden era” of the 1950s and 60s (or later) or today’s modern cards that have chances to pull “relic” and “autograph” cards, eBay is probably the best place to buy this type of sports memorabilia. You can see their sports card listings here.
If you’re buying cards through sales or auctions, research “sold” listings to see what you can probably expect to pay. If you’re going after expensive rookies or star cards (anything beyond $30 or so), it’s probably best to buy graded and authenticated examples. PSA, SGC and Beckett (BVG/BGS) are the three main grading companies.
The Sports Collectibles Shop at Amazon also has a very large stock of cards from sellers all over North America and COMC.com is another option.
Autographs and Other Items
Which memorabilia site is best for autographs comes down to authentication and also what you’re looking for. If sports autographs are your goal, you can, of course, find many on eBay and Amazon. If you’re buying anything involving star or Hall of Fame player, be sure to buy something with a certificate of authenticity from a reputable company such as PSA/DNA, James Spence Authentication (JSA), UDA (Upper Deck Authentication), Mounted Memories or Steiner Sports.
Sites such as Fanatics also have thousands of sports autographs for sale, many of which they have gathered from their contracts with the athletes themselves. Signing sessions help stock the supply of items. Steph Curry is among the players who have exclusive deals with Fanatics. The company’s sister site, SportsMemorabilia.com, is another site to consider.
You can also buy autographed items on Amazon, but be sure to look for the proper COA. Don’t buy from a guy who makes up his own. Again, PSA/DNA is usually a safe bet.
Steiner Sports is also a good place to buy sports memorabilia, including autographs and some game-used memorabilia, although the latter offerings in their online store lean more toward New York area teams. Steiner carries thousands of really amazing autographed pieces and hosts numerous signing sessions each year with athletes. They are almost always offering 20% off with the code SPORTS20 at checkout.
If you’re looking for something more eclectic such as game programs, ticket stubs or other items, eBay is once again a place where you’ll find no shortage of sports memorabilia for sale.