Honestly, I wouldn't bother. I tried to make something with the coin tubes I found, and got some rubber stoppers that I cut down and made a hole in. Functionally, it worked great. They didn't leak, and I cut them down good enough to fit very well. But I couldn't use it. The rubber stank very very strongly and, I dunno if it was just in my head or not, but I swear it made my liquid taste very rubbery. I believe the rubber in syringes is made so that nothing from the rubber comes off in the liquid. Wouldn't be a very good syringe if it tainted whatever you were injecting. That's why I'd just stick with the syringes.
Yes, I can believe that. The grommets I did get had a stronger rubber smell than the syringe plungers. I just wish I could get the syringe plungers w/o the syringes. I hate wasting an entire syringe. LOL. I thought about calling novagen and seeing if they would sell me a bag of 100 plunger rubbers. I don't think the rubber plungers are going to last forever. With the use mine have had so far, I fear they are going to become too soft and start to degrade at some point.