Low-tech solution, make some doorstops, with fabric-covered bricks. Or, look on eBay for cast-iron doorstops.

Commerical applications would call for a magnetic door stop. Screw a small metal plate to the door and attach magnetic door stop to wall.

Same principle is what holds most medicine cabinet doors closed.

Try removing the bottom hinge pin and put a small bend in it (lay the pin on a concrete surface and tap the pin with a hammer). You don't want too much of a bend so take it easy. Try inserting the pin back in the door after every couple of taps until it keeps the door open.

I tried this tip myself after reading it in a magazine recently and found that it worked.