I know that a large bottle of concentrated is only $24 at the local
chemical distributor (picked up).
Cheryl, have you tried just going to the local chemical distributor
and buying nitric acid directly from them? (And diluting it
yourself.) That always worked for me. My experiences are pre-9/11,
but maybe if there are "security" forms to fill out, the distributor
has them. I would go in person, take your business card and photos
of your work, and by being someone who can articulate what they're
using it for, you might have no trouble at all. Another option is to
look around for someone who teaches high school or college chemistry;
they might be able to help you out.