I'm confused at what you're looking for based on your last reply...
Originally Posted by ARV8or
and hopefully with an RV-8 that they might be willing to use (before I purchase)?
this quote makes it seem like you're looking to fly a different -8 than the one you are buying, if so they'll need a waiver from the FAA to charge to rent it and commercial insurance. As has been pointed out this will be difficult to find and Bruce might very well be the closest. I guess theoretically someone could give you use of the plane for free and you'd be legal, but that's probably even harder to find than a plane with the waiver.
Now if you're looking for a CFI to check you out in a -8 you own, it gets much easier. Any CFI can do that no FAA waiver necessary. You'll want to get his hours and contact your broker to make sure the plane is covered but I don't think it should be too much of an issue to find a CFI with enough -8 hours to get Global (and yourself) comfortable. I'm not an expert but I've heard that you don't want to rely on the open pilot clause and it's better to just get the CFI named. I was previously able to get my CFI added to my policy with no additional premium.