I have several steel frame bikes that do not have braze-on fittings on the seat tube or down tube for the attachment of water bottles. I have used the "push-close clamping hangers" from the McMaster-Carr mail order catalogue to securely attach the water bottle cages to the frame. In my case, two of my bikes had 27.2 mm diameter frames (1 and 1/16 inch) so I used the 30075T4 clamp. Along with each clamp, you need to get the "threaded rod adapters" that slip into the clamp and allow you to attach the cage using a 1/4" diameter, 20 thread per inch, 1/2 inch long machine screw. Another of my bikes had a larger seat tube, and I used the 30075T5 clamp hanger. I've used these clamps for a few years now, and they hold the water bottles quite securely. Here is a picture from the McMaster-Carr catalogue page of the clamps:
Here is a link to the catalogue page:http://www.mcmaster.com/#catalog/117/1502/=ckmqie
The clamps are available in a variety of sizes, so you really need to measure the diameter of the frame tube you are attaching it to.