Been looking for a little bit. Although I'm thinking to wire it in. Haven't spent too much time looking into it. But I most likely will soon as I'm having to get mighty bundles up these days.
4 Digit 0 4inch LED Digital Electronic Clock FOR CAR Motorcycle Motor CU3 | eBay
Would be nice if it was fully enclosed, But I could always do that myself. For $5 I can't complain too much though.
Also found this one, Sounds pretty promising.
Hopefully I could squeeze one of these above the dash.