My favorite bag of all times is a disposable German bag designed for barium enemas. It holds 3 liters, has extra large clear hose, has a screw top, and has a small capped nipple that can be used to inflate the bag to put it under pressure using the a bulb for inflating balloon nozzles.
They also have a valve shut off in addition to the traditional clamp.
My experience with them has been that they will last for many, many sessions although they are designed to be disposable.
The large tubing make the flow very rapid if you open the clamp completely and the cap makes them if they fall.
Although I certainly enjoy enemas, my doctor has prescribed (YES, REALLY) that I take several per week and I find this bag perfect for quick, routine enemas. 3 liters is a good size for everyday use.
BTW, I use a 4 quart Klystra bag for very large enemas. 2 quarts is too small for a regular enema but 3 is about right: it is full but not punishing.
A guy on eBay called Medware sells them.
The shipping is expensive to the US but they are the best I've ever used.
(I have no connection with him or business arrangement, of course)
John