As is often the case with missing manuals, there is plenty of help available online, either from appliance manual libraries, or user community forums. One site that combines both is outdoorcooking.manualsonline.com so why not try there first?
You haven't mention which model of the Perfect Flame grill you own, and it will be easier to find the right manual once you find out.
Other online appliance manual collections you can search include manualslib.com, where PDFs of Perfect Flame manuals are available to download.
grillservices.com have seven different Perfect Flame manuals free to download. Meanwhile on scribd.com, a more general online library, a user has posted the manual for the Perfect Flame Vertical Gas Smoker #GS-100, which might be of help
There are also less "specialist" sites where you can ask for help regarding Perfect Flame grills, such as bbq.about.com, ths.gardenweb.com and managemylife.com. These are forums, where you can post a question (once you've signed up) about locating a manual for your grill.
You may be interested to know there are recall notices out on certain types of Perfect Flame grill. Details can be found under this footage of what happened to one YouTube user's grill:
