You have a DeFever which means you have lots of room in your engine room. I have a DeFever 44. I danced your dance (several 12V pumps) before, based on a suggestion on this forum, settling on a Grundfos MQ3-35 110VAC pump. It is large but not much more of a space eater than a system that employs an accumulator tank. The Grundfos has its own internal expansion tank. This pump is a boat miracle. It supplies constant, more-than-adequate volume and pressure with absolutely no change in either. Plumb it, fill the internal tank, turn it on. Done.
You will, however, need a 110VAC outlet to which to plug it in. I ran a new supply line from a spare breaker to a dedicated outlet. I used 10 gauge wire rather than acceptable 12 gauge wire to minimize resistance but that was probably overkill. If you already have an accumulator tank, you could get the same result with a shallow well pump which would be a much less expensive solution. The Grundfos goes for around $625 but you will never have to replace it.