I would love to use one but I have 2 problems:

1) This circuit is going to be inside a closed plastic box with minor ventilation 4"x3"x2" deep.
2) Price, I can't find a good price for those power supplies.

I'm obviously looking at the wrong direction because you mention that there
are SMPS readily available for $5, will you please point me were should I start
looking?

Thank you very much.
Juan