This is what you need. The power seat should connect to the power supplied from the fire wall mounted circuit breaker. The top is a three position connector that would replace the one position connector you already have. It connects directly to the circuit breaker. M&H sells them. The bottom is an expander, it will connect to the existing connector. I don't know of a source other than finding one in a junk yard. You may also need an extension that would connect to the seat harness and the expander.