Try this web page for screws and this one for a variety of various fan screws. You can try this site for the caddy.
So I received my refurbished Dell OptiPlex 9020. When I opened the case I found the exhaust fan separated from the wall of the case. The reason being. Three of the four rubber dimples had separated. One had been sheared off. So I'm assuming I will have to get some screws and screw the fan to the case? Is there a particular size of screw I would purchase? Also, I do plan to install a SSD drive. I do have a Dell SSD Caddy. But it seems the hard drive space is actually larger and larger than the Caddy. So do I have to buy an additional part to install the SSD drive?
Dell OptiPlex 9020 Exhaust Fan Rubber Dimples Sheared off