Gears are usually sliced from extruded gear stock (a really long gear, imagine a silly puddy machine pumping putty through a gear shaped cutter). See this link for a picture of gear stock....
https://sdp-si.com/eStore/GroupHead.asp?GroupID=592
I can't remember if it's the 14.5 or 20 degree pressure angle off the top of my head, but use this link and select from the drop down 48 pitch, and 30 teeth (same as stock) and you've got yourself a long idler gear. All that's left to do is cut to length, bore out some holes for the shaft and bearings, and you're done!
https://sdp-si.com/eStore/Select.asp...SearchPattern=
Modified=00F4DA1210F0C601A7
OR, ask Mike what he'd charge to make you one himself. He may or may not have the time for one time custom parts. But everyone has their price!
Final resort, keep plenty of spare Al idlers on hand. Depending on your truck weight, slipper settings, how you drive, etc... you may fine the AL idlers to be ok.