Something like this.
https://www.whisperpumps.com/Dab-ESybox-Mini-Water-Pressure-System
Attached to a tank would give you fabulous flow and pressure. Variable speed means it only works as hard as hard as it needs to.
Open more taps, and pump speed increases, maintaining constant pressure.
If you go to the pressure boosting section of the site, you will see the major brands, as well as systems designed and built by ourselves in house.
On the site you will find tanks as well, although it's possible your plumber may have more suitable options. If you have time to chat, call the main number tomorrow and ask for Mark. Should be able to sweeten the price also.