I saw boar riders, chariots with wolves, and solo wolves, but no riderless boars. May have missed them though.
I remember see boars somewhere also, maybe pendraken. I'm not sure how they would scale. But since I haven't tried the kitbash yet, they could still be a possibility if this becomes too much of a headache.
And I did see that orcs had the character chariot with a boar. One of the other Beastmen projects I found on a blog actually used that for a Beastmen character. Tracking down 12 of those to proxy the tuskgor chariots though seemed a lot when it was only one figure out of the pack. I figured it would be easier to kitbash some instead.