Frankly, I don't know. Do you have the operating manual for the fireplace? It would typically identify the address for the manufacturer.
Alternatively, there should be an address for the manufacturer on the rating plate in the bottom of the fireplace which would give the city and state (or province) of the fireplace manufacturer. From that I'd start calling to see if you can find a phone number for the manufacturer.
You can try Googling to see if you can locate information on the manufacturer.
What parts are you trying to find and who told you they needed to be replaced? It's quite common for customers to tell me what parts they think need to be replaced based on guesses people have made without having a competent diagnosis of the problem. Most of the time, such guesses are wrong.
More than half the time, all that's needed to get fireplaces working properly is cleaning and matintenance. Another 30% of the time parts need replacement that are widely used and don't need to be ordered from the manufacturer.
So in my view, your first step is being sure that the diagnosis of what is wrong is correct.
Guesswork is a poor method of diagnosing problems with gas fireplaces.