You can buy a new vehicle without a power passenger seat, and replace the passenger seat with a used power passenger seat from a more expensive model. These seats can be bought used from an auto diismantler. A relatively rare item like that might have to be located through a nationwide parts locating hotline; which many wrecking yards subscribe to. Obviously; the most recent model years would be difficult to find through wrecking yards; but 4 or more year old models can be found. You can also buy a new seat from the parts department at a dealership which sells the brand of vehicle that has such a seat (at a premium price).
The seat conversion can be done by a good auto body shop. But you'd need to first make sure the new seat will physically fit in the vehicle. The largest width and height, and the width and langth of the base would be the critical measurements. A body shop may not be up to connecting the electrical wiring; but an auto electrical shop would be able to do that. The whole project might cost as much as $1,500; depending on whether you bought a new or used seat.