Did GM use one ?, the tranny hump is cut in and seam sealed into the stock floor,( hugh hole BTW) the shifter boot mounts with a rubber gasket and steel trim ring to the hump section (for a 62-63 model year) or directly to the bottom of the gear indicator plate on the front section of the console for some late 63's and most 64 models.. there was a rubber cup around the shifter spring to protect it from water and dirt, that was about it...
I have installed my Shiftworks shifter and am looking for a shift boot as well.
Did you have any luck finding anything that will work?
I am also using the early factory console with the round opening... not the rectangular opening with removable face plate. So like you, I'd like to find the boot that seals out everything from under the car.