Good seats are expensive, but there are aftermarket parts available. None are going to be a bolt on replacement for a Kubota, they are usually for 15+ year old Case\Deere\Ford stuff. Go price a complete Grammer seat, and your looking at $800 aftermarket. You can probably make it work, but its going to take some work to match the slope of the floor pan or find a way to bolt it to the sliding mechanism.