I've just ordered an Head Up Display from Kogan this morning.
They have two types, one using GPS, the other via OBD11.
I went for the latter as it gives coolant temp, air flow, battery voltage etc.
Only $69 and seems to display far more than only speed.
Download the manual to see complete details.
My only concern is sun/heat might destroy but it comes with a basic 12/12 w'ty
"Cain't hardly wait"
https://www.kogan.com/au/buy/obdii-car-head-display/