It would not be that hard to make a double ended dildo enema nozzle although I have not done it because I do not have an enema partner.
Get your favorite double ended dildo and measure it for length. Get an electrician's drill. It might be a foot long, but length in not so important as long as it is more than half as long as the dong you are going to work with. Use masking tape , duct tape, or the like and tape the dong to a piece of wood that is at least as long as the dong, making sure it is quite straight in all directions and tape it in enough places so it cannot move.
Then drill your hole right down the center, untape it, turn it around, re-tape it, and drill in until the one hole meets the other. You may have to play around a bit, using the bit more as a router to drill sideways until the two holes meet and water can flow. Then drill a hole sideways half way through at the half way point, put in some sort hose coupling, and you are ready to go. As you drill, pull your bit out every little bit to get rid of the rubber or plastic chips so that the bit is not clogged.
Have fun. I cannot help you to find someone to take the other end of the dildo, though. I guess that is another part of the do-it-yourself project.