The bottom of my fish filter intake tube, the part with the little slits in it that keeps big things out of the tube got lost while I was moving. Does anyone know of something else I can put over the bottom of the tube?
She means the intake strainer. A bit of sponge, mesh or clean tights can serve as a temporary measure to cover the inlet. I use a spare mesh bag (the sort you buy to hold loose filter media) over my siphon tube to stop fish getting sucked in when draining the tank.
Depending on the make of filter you can probably order a new spare part, e.g. if it's an Eheim, it's usually quite easy to get Eheim spare parts from Ebay or other stockists.
That will work fine for the meantime. Depending on how fine the mesh is, you may find plant leaves and other debris stuck to it. I'm cycling a dirt tank right now and I'm continuously knocking bits of soil off. The mesh may clog a little, but if you knock off any debris, you won't have an issue.