The problem is that a standard sized humbucker is wider than an ashtray bridge plate. Add the ears for height adjustment and it gets even wider still. Look at some teles with a bridge humbucker in a plastic mounting ring. The ring is wider than the bridge.
There are a few around for six saddles, but if you look closely they're wider than a standard Tele bridge plate. I think it would look weird to have the raised edges ashtray style that wide so they just aren't offered.
TV Jones offers a 3 barrel plate for their pickups (which are smaller than normal humbuckers) but it doesn't the raised edges. And, obviously, it will only fit their pickups, but they do have a pretty wide selection.
It's true... humbuckers are too wide for the standard tele footprint. The Rutters bridge has an adaptor plate for a standard humbucker that bends the ears in and mounts to the bridge like a regular tele pickup... I've seen pictures and it's pretty darn cool.