Can you please explain that a bit for me?  I was under the impression
that most Rx's could be read (neutralization) rather readily, no?

Actually its a simple matter to read the prescription of an existing
pair of glasses.  "Reverse engineering", as you put it, would be easy.

Now, as to where you could send your old glasses based upon an
internet contact, I don't know but I'd imagine that shouldn't be too
hard to find either.

Another approach would be to take your glasses to a local optician or
optometrist, ask them to read the prescription with their lensometer
and write it down for you (a simple matter taking about 1 minute), and
then you could use that to order another pair with the same
prescription from an optical site on the internet.  Sites that will
sell you glasses if you know the prescription are easily found on the
internet.