I usually just hope to find a cheap panel on ebay that says it will fit the model I need a replacement for, especially for old laptops. Another option is to get a broken laptop of the same model who's screen still works. (the second option is not so easy for newer laptops)
If you do search for parts on ebay - the repair shop I work at, we tend to use Screenaid if they have the part. We might have had 1 or 2 faulty screens out of the hundred or so we have ordered from them.
I'm not necessarily looking for the "cheapest" panel and I want a company that stands behind their product should something go wrong. If that means a few more dollars, so be it.
I will check eBay for Screenaid. Thanks for that tip!