I have a blue nylon horse harness for sale. I've only used it to ground drive a couple times… it hasn't even been hooked up to a cart. The only part that looks even remotely used is the fleece cover for the crupper.
It's tough, durable, and easy to clean. It'll be great for training and driving on trails. It comes complete with blinders, reins, half-cheek snaffle bit, and several pads. The only other things you will need are a back pad and something to connect the breeching to the crupper (a zip-tie will work for this).
I really love this harness and I'm only selling it because I don't have the money for both a cart and a new saddle and I have no use for it without a cart.
I paid $120 for the harness, $30 for the bit, and $100 for all the pads. I'm asking $199, but I'm open to offers. You can reply on here, PM me, or email me at firstname.lastname@example.org if you're interested. You'll probably get the fastest response by email.