There are no active auctions on eBay at the moment, but anyone looking for a CO scale Bessie should create a saved search for "Tudor Rose Ford 1910
As you can see from the photo below, the model (which is naturally all black, and needs to be painted) is probably 1:12 scale instead of CO's wonky 1:13, so it's every so slightly too small to make a figure sit down fully in the driver's seat, but it's not that noticeable when you've just got the 3rd Doctor standing next to it. While it's not a *perfect* Bessie replica, it's the closest thing tyou're ever likely to find pre-made in the (mostly) correct scale.
The model does come with a spare tire, but it's missing the spoked rim part and is mounted on the side of the car rather than the back. This divot is easily filled and painted over, and if you have materials handy, you can take a clay/plaster impression of one of the other wheels to create a mold for building the spare. Then all you need to do is attach it to the back. You'll also need to carefully cut out the doors from the back seat area, though the plastic on this model is very rubbery, so this is easily done with a simple Xacto blade. The windscreen should also be larger, though that's easily replaced with a thin sheet of Lexan cut to the appropriate size. If you really want to get accurate, there should also be an extra curved hump between the bonnet and the windscreen where the upper headlights should be remounted in a lower position. I suppose this could be sculpted out of milliput, cardboard, or this sheet plastic.
I would advise making all your physical modifications you plan on incorporating into the design first before you start painting. I made the mistake of painting mine as soon as I got it, but because the model is so flexible, the enamel paint just flakes off as soon as you start pushing and pull on it, creating a big mess.
I may eventually release a 3D Printable Mod Kit for this model which will include the bonnet extension, spare tire, larger windscreen, and a few other cosmetic changes.... or possibly just try scanning it and using it to build an entirely new piece-together model from scratch.