Thanks guys!
The grate material came with the bench it's on. I found the bench on Craigslist. I guess it was used in a trade school originally as a hydraulic test center. Under the grates is a slanted bed with a drain hole in the center.I'm not sure if it'll have enough drainage for the amount of coolant I plan to spray around in there eventually though.
I actually got some of that gasket material (the black/rubber gaskets for 10 series extrusions) but there's no way it would ever fit with 1/4" panels (even though it clearly says it will in the auction description). The slots aren't much bigger than 0.25", and my panels are 0.22" (I think). Maybe they sent the wrong stuff?
At least I couldn't make them fit. Maybe there's a technique that I don't know about... I haven't tried coating them with oil yet.