That's hard to believe... I'm going to have to check my local drugstore the next time I actually go into the store, (been using the drive up window...).
In the past I had seen them, naturally they weren't called 'enema bags', but basically hot water bottles, still well made of a heavy rubber, but with 'accessories' included for female douching. Just a different plug to connect a hose to so you can hang it upside down, then a clamp, and two different nozzles.
If you're talking about the disposable, 'real' enema bags, I had never seen them in any drug stores I visited. I had seen them in medical supply stores... stores that specialized in canes, crutches, wheelchairs and the such.
In fact you would be surprised at what all they carried! Some items behind the counter, requiring a prescription to get. I used to go to one medical supply store some years ago that actually sold catheters over-the-counter. Something I thought a prescription would be needed to obtain. But they sold them, and for a lot less than Internet companies that deal with such items sell them for!
I would imagine obtaining certain medical items would vary from state to state.
I used to purchase 'cases' of disposable 3 liter enema bags, with balloon rentension nozzles on a wholesale basis and sell them on ebay. If I remember, I had probably sold one each and every week when I listed them. People used to get in bidding wars over them, not knowing that I would have another listed the following week.
In taking a look at ebay now, I see that there is still a lot of listings for enema suppies and equipment, from the drug store hot water bottle type, to gallon bags, the squeeze type bulbs, tubing, all kinds of accessories, even seen a '6 quart' bag on there. 'Really' don't like promoting ebay! But when you can't find something anywhere else, that's always a last resort.