I think what you are referring to is a type C automotive fitting. It looks strange as most of have always used type D fittings.
Both are available in 1/4" NPT.
Typically you will have one male and female fitting. THe male is used for filling the system from an external source, such as would be needed for towing. The female fitting will allow you to use the onboard compressor to air your tires etc.. (see post 26 in this thread http://www.irv2.com/forums/f258/what...-107949-2.html
On my coach I changed out the coaches fittings for Type D, rather than have two different style wire hoses laying around the shop. If you can't remove the female fitting on your coach you could simply change the male fitting on your air hose to match the Type C female fitting.
Both fittings are common and can be found at Lowes, NAPA, etc.. or ordered on-line. Probably easiest to pull up to Lowes or NAPA and take a couple fittings out to see what fits. Be sure to test with female fittings placed on to the coaches male fitting. If you do it the other way around you will feel a strong blast of air.
I've included a couple pics. the one on the left is the Type D, leaving the one on the right to be the Automotive Type C.
US Navy Vet, Liberty Tree Member of Oath Keepers, NRA & VFW Life Member, Alaska EMT.
2009 Safari Cheetah 40 SKQ
2009 Winnebago Chalet 231CR