The best shower head in my opinion if you have low water pressure is the shower head Delta 52652-PK
You can buy the Delta 52652-PK shower head online or even at Home Depot, Lowes or other hardware stores.
Some other good shower heads for low water pressure are the below listed shower heads.
Delta 2-Spray Shower Head Water Amplifying.
AquaDance 7" Premium High Pressure.
YOO.MEE High Pressure Handheld Shower Head.
Speakman S-2005-HB 2.5 GPM Adjustable Shower.
Aqua Elegante 3 Inch High Pressure Shower Head.
G-Promise High Pressure Shower Head Premium.
SparkPod Shower Head - High Pressure Rain.