Best fit? Factory pillar tweeters with the factory pillar cutout from a truck with Premium Sound system (Infinity). Autowreckers or Ebay can probably get you fixed up.

Second choice? Crutchfield has quite a few listed for 2 Gen Ram:

Crutchfield Link

I've never replaced my A-pillar tweeter, so I can't comment on the aftermarket tweeters. It says "modified fit" on all the listings, but that can't be too bad?