Cannot think of any production cars that use any QC type gears that you could adapt the housing from. Making a housing is not a big deal if you have access to a decent size milling machine etc- however if your going to pay market rates for someone else to do all or any of the machine work your $1200.00 will evaporate real quick.
Some FWD 3liter Nissans have a pair of gears that are about 120mm c to c on the auto trans version where they drop down to the final drive pinion- these have a helical cut and a tooth count something like 41/42 so they dont repeat, but thats the only one I can think of .
If you dont want to change the ratio you could always use two of the larger spur gears from early VW Combi Hub Reduction for a 1/1 deal, doubt you would ever break those plus everyone would hear you coming & going