Hi Thomas,
I'm not a GTW modeler, hardcore or otherwise, but I am a fan of the Central Vermont. My understanding is that both roads used the same design, or at least a very similar design, for their wood cabooses. Photos would seem to bear this out, and at least one website found in a quick search states that they are the same design. As usual, caveats apply about the validity of claims made on the internet. If you accept that the cabooses are the same for both roads, then you might look for one of the Mullet River Central Vermont caboose kits as a viable substitute for the GTW. Here's a link to Marty McGuirk's CV blog, if you scroll down he has a photo of one of the MR Central Vermont cabooses.
There are a few issues though. Mullet River is no longer in business, the kits are not in production at this time, and they are relatively hard to come by. I believe that the artwork and tooling was sold to Des Plaines Hobbies several years ago, but I have no idea whether there is any realistic intent to bring the kits to market again. Secondly, it's a craftsman kit offering, rather than RTR. Whether the kit is a logical choice will depend on your skill set and inclination. And there are miscellaneous other considerations: the kit is typically pricey, and you will need to source brake rigging, trucks, couplers, and decals.
If you are interested in the Mullet River kit, I can get you some photos of the box contents to review.
Good luck,
Jim
