EBay is just about the only way of getting vintage enema and douche equipment As to NOS, it i almost certainly a fiction.
50-odd years ago, virtually nobody ever bought a bag just to look at it. Bags etc were, and probably still are, bought because they were needed. (A couple of times I've been in a pharmacy and seen or overheard a mom but an enema and a bedpan for a sick kid. It was completely obvious the bag was soon to be filled and the kid would soon thereafter be on the bedpan, pooing)
I very much doubt there is any significant risk from using a bag from eBay, provided it has been well cleaned I clean every part of an eBay purchase upon receipt by first completely disassembling it, then a 1 hour plus soak in warm water w/ dish detergent, a rinse, another 1 hour plus soak in Clorox solution, another rinse, then hanging to dry. Be sure the bag and hose are completely filled with the solutions. I do no put any metal shutoffs in the Clorox as it may cause them to rust) Do no use hot water as it may cause white ‘rubber bloom’ on the bag and hose. Even there precautions are likely unnecessary, as microcritters don't live on surfaces of 50+ years
Finally if you see a bag listed as NOS, there is an easy way to tell If the hose is attached to he bag or nozzle, it's been used These parts were NEVER assembled when the bags were new.
So, if you crave a vintage black, curved, hard rubber douche nozzle inserted wherever, eBay is pretty much your only option