Some PCs are still available with Windows 7, although they’re vanishing fast. Search a site like Amazon for “Windows 7 laptop” and you’ll probably find them.
The big problem with purchasing a laptop with Windows 7 is that it will likely be rather old. It’s now been 14 months since Windows 8 became generally available, so all these laptops will be over a year old. When you consider the huge advances made in hardware in the last year, particularly with Intel’s Haswell chips and their extremely improved power efficiency and battery life, these don’t look like such a great deal.
Seeking out an old laptop is a dangerous game, as you may end up paying significantly more than the laptop is worth. Be sure to compare it to new models and verify that you’re actually getting a good deal — new Haswell and Atom laptops are becoming surprisingly cheap. You’d probably be happier with a longer-lasting, newer device, even if it comes with a version of Windows you don’t prefer.