Do they make interior door knobs that can be locked from both sides? If so can someone point me to a web site with them. I'm looking at a pullman bath set up and would think it would be best if the doors could be locked on both sides.

What Is The Purpose Behind The Double Sided Lock?

The reason I'm looking at this is the doors to a pullman bath from each room connecting to it. This way the person entering the bath can lock the door from the other person who might enter it from the other side. I'd also like each person to be able to lock the door from their room side so that if they don't want the other person to come straight through the bath to the other person's room they can lock the door.

This is the type of locking system used in adjoining hotel rooms. Obviously they are made but you won't find them at Home Depot. Try a supplier of commercial hardware or serach the net for a local supplier.

You could just put a simple bolt on either side.

Labman is right about the simple sliding bolt lock. If that did not fulfill your needs just use a deadbolt lock that takes a key on the bedroom side and a turning knob on the inside, that way if the people in one bedroom tries the door and it won't open they will know it is locked. And if the people in the other bedroom forgot and left it locked the other bedroom people can unlock it with a key, hopefully there is no one in the bathroom.
You can buy these at any hardware.

Think i found you a link. Beeson Hardware High Point North Carolina - oldest Hardware Store (http://www.beesonhardware.com) this is a company where i live and they specialize in comercial and residential hardware. Obviously you'll have to order it, there in highpoint north carolina
ive bought a lot of odd hard to find knobs from them, good luck i think you'll find what you need.

Thanks for all the great feedback. I've got some ideas of what to look into now as we select doors and locks!