where can I see Psalm 40, verse 2, written in Aramaic?

As far as I can tell, the Aramaic Bible is (sometimes) called the Peshitta.
(see reference at http://www.peshitta.org/initial/peshitta.html)

There is a searchable version online at
http://cal1.cn.huc.edu/searching/targumsearch.html -- You can select a
book (Psalms), chapter (20), and verse (2), then check the box about
displaying in Aramaic.  The only caveat is that the Aramaic will
display as jibberish unless you have the correct font installed -
though I think the site does give information on installing the right
font.

If this doesn't work, try searching under "peshitta" or "peshitta
psalms" - it will at least give you links to online bookstores selling
books that have full Aramaic versions of the bible (though they're
sometimes rather expensive).

The best starting point to look for an answer is
http://www.yourdictionary.com/elr/christ.html