Look on Ebay or Amazon for something like "Universal to US Plug Adapter" with a US 2-prong male plug. This is an adapter that accepts many external US and international male plugs via its own female sockets (it supports US 2-prong polarized or even US 3-prong polarized) and at the other end of the adapter there is usually a US 2-prong non-polarized male plug. Indeed, most of these (or even perhaps all?) universal adapters have at one end a US 2-prong non-polarized plug; I believe they do this on purpose to make it more universal, for a 2-prong non-polarized plug can be inserted into either a 2-prong or 3-prong outlet, polarized or non-polarized, grounded or non-grounded.
Good luck, and keep us posted!
P.S.: By he way, these adapters are usually very cheap, sometimes including free shipping.