Manure forks usually have a number of tines. If you have a tooth bar, replacing the teeth with longer tines would work. You might have to custom build something. You'll have to make the tines strong enough to support the load. I'd look into a design that extends back into the bucket and sandwiches the upper and lower surfaces to spread the load out.
If you don't have a tooth bar, you should be able to come up with a clamp on arrangement for the tines that would work.