I had a similar issue to add VMWare drivers for 64bit in my Win7PESE. The solution I found was easier than I thought it would be. When installing VMWare Tools it adds all necessary drivers to your Windows System. A copy of these drivers is added to C:\Windows\System32\DriverStore\FileRepository (Assuming your Windows directory is directly on C Drive). So I sorted by date and found the subfolders that had the same date as the installation of VMware tools.
Using the Driver Integration Script (included in Win7PESE), I copied the drivers to the 64bit script folder (In my case %GlobalTemplates%\Drivers_x64\ ).
It's possible if you already have the firadisk drivers installed, you could copy the required files from your driverstore and add them to your Win7PESE disk using the Driver Integration Script as I did.
P.D. If they are 32 bit drivers, copy them to the 32bit script folder.