Some time ago, I bought a syringe from Amazon that has a special attachment to flush the ears. This works great, only the syringe slide is much too weak and broken after a few uses. So, I have now created a more stable. 

Instead of using the rubber from the old slider, I used two O-rings (19 mm x 2.5 mm). To make the O-rings easier to install, the tip of the slider is removable. I used an M3 10 mm Allen bolt and a nut embedded in the new slider to attach the tip.