It depends on what is causing the pressure loss?
1-Is it galvanic corrosion?
2- Is it city pressure/well pressure that needs boosting?
3-Do you have a partially crushed main or a partially closed valve?
4- Is it just the shower head full of mineral deposits?
5- Did you take apart the shower body to ensure that a particle of old washer may be the culprit?
6- Are your pipes over sized so you get the volume BUT have a severe pressure loss
7- Are you talking Volume or pressure
8- Did you put a gauge on the nearest out let to find your actual pressure?
9- If this is a high rise building is it gravity fed and what floor are you on?
10-Do you already have a PRV located on the main of your in coming water supply line?
11-Was this a chronic problem of just lately?
12-Was any new plumbing added to this system?
13-Did you bother to check for as flow restrictor inside the actual shower head?