Endeavors are great vehicles! We bought a 04' for my wife and aside from the low gas mileage it has been an excellent car! The only problem we've had so far is replacing the propeller shaft but I've read that those are a pretty common repair on the Endeavors.
As for aftermarket accessories, there aren't much. If any. Your better off looking into OEM accessories like the fog lights, rear mud flaps, grill guards, etc. Other than that you can look into having a custom exhaust made, Universal HID kits, etc.
Check this site out for some OEM accessories...
http://mitsubishi.dealerfit.com/stor...t1272_1274.php