I have a big TB that has a very slow and steady canter, I actually had someone interested in him some time ago for vaulting but they didnt end up coming to see him.
He is only 16.3 ish though and not quite a WB build but he is bigger than the average bear.
He's in paddock shape so I would be negotiable or I would lease him to an exceptional home if that'd help. He has leg scarring so I hope that isnt an issue for you either.