Almost all new faucets and shower heads have a flow control device installed.
If you want to retrofit an existing aerator contact either Creed or Sexuer or one of the better faucet replacement parts stores.
During the greater NYC toilet change out a lot of aerators had these discs that also limited the GPM rate.
If you live in a big city either the gas supplier Or the local water department will give you several of these devices for free, reasoning conserving water especially hot water conserves natural resources.
You can also contact your local plumbing supply.
If you have a licensed master plumber in your area they can instal a flow restrictor directly in the supply piping for the faucets in question with less possibility of sediment causing a blockage problem.
I install some devices on the out let of hot water heaters/boilers to make sure the flow rate does not exceed the make up so thus insuring my accounts have almost a constant supply of hot water when needed while still saving a bundle on fuel costs.