Sadly, they went away not too many years ago after being in business since before the Civil War. Chassis parts are fairly easy as they will be tha same as whatever make/model the bus was built on. Mine, for example is on a 1946 Chevy 1-1/2 ton truck chassis and I can still find most parts through dealers, vintage shops or Ebay.
Body parts (and any of those that Wayne fabbed) are a different story. Your only hope there is junkyards and again, Ebay. I am constantly amazed at how much obscure stuff shows up there. Post war stuff is MUCH easier to find and there are several "Old Chevy" dealers online. If you are in need of anything in particular, lemme' know and I'll dig up some of the suppliers I have come across.
Would love to see some pix BTW.