Any aeronautical chart shows the magnetic variation, and is probably more
frequently updated than any other government type chart (every 56 days). I
wouldn't worry about the changes too much, since they may amount to 1 or 2
degrees in your lifetime (in the latitudes for the continental US). It's not
worth worrying about too much at HF, since most of us are using antennas with
beamwidths that are 25-60 degrees anyway.
Go to your nearest airport (the smaller the better), and ask for some
recently out of date sectional or WAC charts for your area. They will be glad
to give them to you for free. They can't sell them, and it will save them
from having to throw them away.
For what it's worth...
4NC (Due to another typo, I have a vanity suffix only now!)