Perhaps we can help. I would need to see what your Joomla site looks like.
Mostly, the issue is what graphics your after incorporating. We use Mambo, and a Help Desk, so we chose to ingerate to a Help Desk with Wizards and Help Tickets. However, like I say your request is more of a graphic nature.
That is, the graphics from your website, Joomla or any, can naturally be incorporated. But size of logos, slogans, etc. are a factor. So likely, the big thing is resizing, etc.
Take a look at our integration to our Help Desk. Try using the CHAT even if we are not online, so you can see our graphic implementation inside the CHAT system. We can do what you want for sure. But, after a look see, you may want to consider the value of a Help Desk implementation, and link to the Help Desk as we have done.
You see, our goal is to deal with a lot of volume, but have very few % use the LIVE HELP. So using FAQs, and WIZARDS, we plan to step-by-step eliminate the biggest part of CHAT requests in the first place. In your case, just something to think about.
Either way, if you would like a quote, I will need to look at your website and see what the graphic issues might be, if any. So drop me a line, and I'll take a look see at your Website, okay?
NOTE, we do not "Go Live" with our Monitoring Service for a few more days, but we are never-the-less trying to keep an OPERATOR on standby most of the day to watch the CHAT. So you may get luccky and reach one of us anyway.
Have a great day.