The small round speakers on top of the dash are what size? Is there a company out there that sells speakers for this fit? Thanks!

The are 2.5" speakers. JBL used to make a set, # GTO220, but I do not know if they are still in production or not. Here is some instructions... Stealth316

they're not in production anymore. however, you should be able to make an adapter to fit any size tweeter. just get a plastic milk carton or something rigid, cut out a 2.5" circle, then cut another hole for the new tweeter.