Not sure how hard you looked or what e-tailer you are buying from but here are two possibilities...
Check out the HP Pavilion dv6-2180us NoteBook
which seems to fit your specs.
For a lot less money, there is the Acer Ferrari One FO200 netbook
but sans the DVD drive.
Aside from the pre-loads and bloatware, the HP seems like a nice machine...although Acer is nothing to sneeze at either.
My experience has been, especially with portable devices, that it is ultimately cheaper to buy a laptop or note/netbook than it is to build one.
However, if you insist on building your own portable, there are sites like www.directron.org, www.ocztechnology.com, and http://laptoplogic.com
where you can purchase parts, barebones, and DIY kits.