Does it need to be Windows 7 or are you buying it because people have said bad things about Windows 10? I have Windows 7, 8, and 10 computers. On the 8 and 10 computers, I install Classic Shell. They operate almost the same as the Windows 7 machines.
Otherwise, I use Slickdeals to find a lot of my tech. If you can monitor for a few weeks, you can often find a deal.