You can take a micro-SIM and simply cut it down using a pair of scissors to nano-SIM size and it will fit in the iPhone5. I just did it, and even though nano-SIM (4FF) is in fact thinner, the normal SIM thickness fits with no problems and works.
Don't hold me responsible for breaking your phone or your SIM if you try this, just saying it worked for me.
P.S. Obviously, yes, crap maps and all, I have to succumb to the pixie dust they use on their new products - they are just so shiny. Sorry.