While you are looking for a block (and cursing the SOB who fibbed to you), I would do some research and a little looking for a decent brazer in the neighborhood.
If you decide to try to chemically repair versus weld or braze, I would try this route. (Assuming the pipe is secure and you do not feel that the pipe could work loose or cause further damage.
-Clean it up as best you can, then clean it more.
-Tip on its side so any putty you put in, stays in.
-Find something that will just fit in the hole. This only has to stop epoxy from oozing in. I am envisioning steel wool or something. (I am kidding when I say paper or chewing gum, but it should be small and not create a big pocket when it deteriorates) you may even be able to use the next step if its firm enough.
-Coat as per directions with a thermosteel like product ( http://www.aremco.co...p-metal-sealer/
-After a complete curing, I would probably create a reinforcement area of a good epoxy (JB, quik steel, etc. see if one has a temperature rating that is better.). I would be liberal in its size and apply for maximum adhesion with little regard for aesthetics as this may well be your last chance to try to save the engine.
-I would also consider top layering in some coarse stainless steel screening in it to improve structure, but only if it will not create a weak spot or promote delamination.
Some may worry about heat dissipation, especially near the exhaust port. I am thinking that with as much crap as we find in the fins on most engines, this is an acceptable risk versus no set time and a probably junk block anyways.