One company which does make some, are QRF who do some relatively affordable German horse carts, so I invested in a few to lug my 15mm Germans stuff around.
Here they all are, moving along in a column. What a great target for Jabos. I was a bit disappointed to find they are the version with pneumatic tyres, but if I really cared, I'd buy some Irregular spoked wheels and convert them. I clearly didn't care that much.
These are nice little models with perfectly useable draft horses and a couple of crew figures. Obviously any old sitting figure would do, and one of these chaps has a somewhat anachronistic peaked cap. Again, if I really cared, I would do a head swap or a bit of judicious filing down of the offending headgear.
These carts aren't very sophisticated. Just a box on wheels. It was very easy to assemble, but like all horse transport, it takes up a huge amount of space. I can see why everyone got lorries instead, but at least if hasn't got a four or six horse team.
And there it goes, off into the distance. I did these all panzer grey with a liberal coating of mud and dust so they are good for the whole war. I do pretty much all my German softskins that way now as there was still plenty of grey transport knocking around in 1944.
So, if you want some horse carts, these do the job, but if you want spoked wheels, you'll have to look elsewhere or dive into the spares box. 20mm gamers are somewhat better catered for in this department. It subsequently occurred to me that these would be pitifully easy to build our of plasticard, and Irregular do both spoked wheels and separate draft horses. Alternatively you could just buy a six horse limber and make up some wagon teams from the horses (there are horse drawn limbers around and oddities like Tchankas).