Years back,at least,Junction City was known as a place where you could buy nearly anything if you had the money.
Even stolen items from quarrys,oilfield,etc.,that were too "hot" to sell elsewhere could be sold or fenced in the area."Anything" that someone could steal from the Fort would be available around there,too.
I don't think it would be that much of a problem to get ahold of blasting caps,or anything else,if a person is willing to steal or pay blackmarket prices. :(