Pioneer system - Rear deck speaker replacements

Did a search, but didn't find any info regarding replacing the rear deck speakers. Whomever owned the car before me blew them up and I am wondering if anyone knows what I can use as replacements?

I think I remember someone saying they used specific clips that won't necessarily work with just any speakers.

Any ideas or anything anyone has used that is compatiable with the Pioneer 9 speaker system? Or what is the stock part number for those speakers and can I get them somewhere other than the dealer?

Thanks