Presume you mean these things?
Low shower pressure? The Shower Power Booster fixes it in minutes. DIY install, no electrician, 95% less energy. 4.9★ on Trustpilot. As seen on Dragon's Den.
showerpowerbooster.co.uk
I have an automatic one on a kitchen tap hot feed.
Works well. In hindsight, I would have bought the double pack and boosted all the HW.
We have a fortic tank (cold and hot in one) in the loft which is not suitable for normal pumps.
Easy to install