Are you sure about the pull start? I asked the cust service guy about that also and he said he wasn't aware of any pull starts that would work.
I will look up the part number tomorrow at work and post it. I had ordered a guy a pull start for his Pro28, we ordered one for a "AE Pro 4.6" and it comes with a bunch of parts that make it work. I still have the part numbers on the work computer.
As for a blank backplate, I don't know of one....but I am sure the pull start is possible.