Amazon basic cables.

http://www.amazon.com/AmazonBasics-USB-Cable-Micro-Meters/dp/B003ES5ZSW

Sure.

So I used this as a guide.

The petRockBlog and /r/raspberry_pi were also helpful resources.

I bought a Raspberry Pi B+ Complete Starter Kit, 2 Buffalo Classic USB Gamepads, and Zune A/V Output Cable. The A/V cable has to be compatible with a Zune, some A/V cables like this won't work. I learned that the hard way. I also bought a Mini Wireless Keyboard. A keyboard is required for the setup (any keyboard will do). I got the mini keyboard so I could have a keyboard in my car to troubleshoot potential issues while on the road. It's optional, but I recommend it.

Then I just followed the guide (mentioned above) to set up the RasPi with RetroPi, then plugged in all the cables, and bam I had a retro game console in my car.

NOTE: Instead of the 2.5A Power Supply included in the kit I used a standard micro usb cable plugged into a USB slot in the center console to power the RasPi.

My sister got the amazon branded one $1 cheaper, and she really likes it.

Although, not sure where you live, but check out MonoPrice if you're in the States. Their cables are super cheap and pretty damn good quality.

I buy all my hdmi/ethernet/etc from them. If you're in California, their ground shipping usually only takes a couple days.