Unfortunately everyone is on the Win 8.1 bandwagon & 7 is hard to find (except on refurbished machines which I don't think you would want), but it is quite usable with an alternate shell (classic shell, start8, etc.).
I am partial to HP business machines. In my experience the machines become technologically obsolete long before anything breaks on them.
The HP website will have a changing list of business machines that the company is fairly heavily discounting-there are currently several laptops, most Windows 7. Prices vary, but most start with an 8 rather than a 7. However they come with a three-year warranty if that is important to you.
There are very few laptops with that specification. However, I would look at Dell Latitude E5430 with Intel i5 processor and Windows 7 Home Premium for $712 (configure.us.dell.com/dellstore/config.aspx?oc=slctj1&cs=04&s=bsd&dgvcode=ss&c=US&l=EN&dgc=SS&cid=274303&lid=5130719&acd=12309196727460804).