They can be hard to find sometimes... but it looks like there are some up on eBay and on Reverb. The GB7's only come in one size so if you get the right version it should fit.
Thanks again, I think it will fit the hole no problem, but aesthetically, the post is tapered and smaller than the rest which I may be able to live with. I am going to check reverb, but if you are correct, then I'll just have to live with the smaller post.