If your in California of course it is going to be really difficult to get draft tack, you may have to scour on line or order it from a draft tack store, hoping that it fits once you do get it in the mail.
Ask your farrier if he will even do a draft horse, as many will not or they do not know the hoof make up of a draft horse. This is really important as many drafts have ill manners once it comes to their hooves, they lean, and they will jerk and pull their hooves out of your hand, so you need to work with them each and every day.
Can you ride them? Of course you can and anyone who said their backs were weak apparently never drove one or used it for farm work. I also use to show my draft mares in draft shows and the town shows as well as state fair. We did well but I got tired of the abuse and ignorance I saw.
This is Smoke, who is a registered mare:
You have to keep in mind that they do take a bit longer to cool down, they do often times have hoof issues, they are hard to board as many places don't like how hard they can be and often are, on a fence.