Williams makes them. The Williams Gun Sight people have made bases, peeps, beads,ramps, all kinds of sights for many, many years.
Give them a call at 1-800-530-9028 and talk to them. I'm sure that they can help you make the correct choice. It's an easy enough task to put a peep sight on a receiver, either the 5D or the Foolproof, but the question is going to come in on what front ramp and front sight you're going to need for the proper front sight height.
You'll need a gunsmith to install the front sight ramp.
