Any USB/FireWire disc drive will work. The only one I am unsure of is the Apple one they made for the MBA in the late 2000s/early 2010s, there are conflicting reports on that. You can get an el cheapo one for $10-$20 no problem though. Even if it doesn't work you aren't out much.
I'm not quite sure what a Mid 2008 MacBook is referring to, is it white plastic or aluminum? I know that on the aluminum ones it's very simple to replace the optical drive if you are willing to, you can even add a second hard drive in place of the optical.