Try these sites:
www.trackofthewolf.com
http://www.dixiegunworks.com
http://www.americanrevolution.org/reenact.html
The best way is to talk to the re-enactors. You might find a good used one for sale and they can give you better advice about which manufacturers are best. Be prepared to spend some money. I bought my Charleville musket 24 years ago for $350. Today, the same musket goes for over $1000. Then there's the clothing and other accessories. Again, talk to re-enactors.
Let me tell you, 18th century clothes can be very uncomfortable in the summer. Most were made of flax or wool since cotton in that era was an expensive, labor intensive crop. Unless you wear a normal size shoe, they can be tough to find. I take an 11EEEEEE and I have a damn tough time finding shoes that will fit. I have had a couple of pairs made for me but few cobblers do that sort of thing anymore.
The hobby is only as fun and satisfying as you make it but I've been doing it for a long time and I still get a kick out of it. And make sure you get proper training in loading and shooting. I've seen some nasty accidents during battle re-enactments that were caused by careless loading and men firing improperly cleaned weapons.