ebay and domiracer.com are the two places i have been getting parts for my 1965 mountaineer 100. essentially the same as your cadet except mine has two rear sprockets and a smaller seat. try domiracer if you prefer new parts. they seem to be pretty well stocked.
I found this guy that is selling one, He basically has the complete frame and wheels attached. He has the engine and all related parts in a couple boxes.. He wants $500 dls for it!! He said he has all the parts for it. Let me know if interested I can send you the link.. P.S. I dont know the guy, so dont think Im selling it for him.
I would buy it from him but he's somewere in the east coast.