Have you looked at FlashChat
Darren's Script Archive ? I had a quick look at Chat Blazer and it seems reasonably similar — there's a demo at
FlashChat v4.8.3
It will cost you the princely sum of $5 to buy ...
BTW, if you preview any URL hyperlinks you add to a message, then Switch Editor Mode to reveal the raw HTML, you can edit the string displayed and then re-preview — what I won't know until I submit this reply is whether my edits will be maintained!