Just a small note: If you have one, then I’d wear a regular point or spread collar white dress shirt instead of an OCBD. It’d be more formal for the occasion. Black dress shoes, too. But that’s only if you have the option/money. Don’t stress it if you don’t, it’s just a suggestion.
As for a tie, I think Put This On covered it pretty well. You can go with a Prince of Wales, houndstooth, sheapard’s or Macclesfield check tie.
Where to buy? Depends on your price range. Broke? Try The Tie Bar. You could also hit up eBay and probably easily find something. If you have a decent amount to spend, there’s quite a few options. On the real high end, Drake’s and Ralph Lauren Purple Label should definitely have options.
Going a step down to around the $90 range, I really like the Kent Wang six-fold silk ties. He’s got a glen plaid and Shepard’s check for $85. If you’re looking for something a bit more seasonally appropriate, then give Fifth & Brannan a look for their black and white houndstooth check wool tie for $92.