I work at a retail pharmacy, i wouldn't try sending it to another online company or running it by your insurance a second time. But I think you could easily get away with going to a retail pharmacy and paying cash for it.
a caution i can think of is some states (like Nevada) have a "secret" registry of all controlled and narcotic drugs (schedule 4 or less) scripts that are filled. I've never heard of anyone getting busted from it though.
Tell the tech at the pharmacy not to run it on your insurance (I do it for people) but i would go to a pharmacy that doesn't have your current insurance on file just in case the tech forgets.
Not going to a big chain pharmacy wouldn't hurt either.
I work at a small chain (8 pharmacies) and there is no way we would be able to tell if someone had it filled somewhere else if we didn't bill it through insurance.
hope that helps you out