They aren’t difficult to make on your own and you can make sure you have ones that are usable. As @Cotty indicated, you can manage with a single turn as a component and array it.
If you do find threads in the 3D Warehouse, make sure they are internal threads and not external threads that have just been turned inside out.
FWIW, here’s a quickie example internal thread. I have modeled it with the back faces out (green is my default back face color) so it can be stuck into a part later. As a component it would be saved for future use.
You might also want to chamfer the threaded holes to make the lead into the threads easier. Cones can be used for that.
