My palliative care nurse gave me a bung and a number of 10ml syringes. Over time the markings wore off, so I asked for more syringes. None of them fitted. She did this 4 or 5 times, and in the end I purchased some from Ebay. They too didn't fit. (All too loose.)
Best thing to do is to go to a pharmacy and ask for some bungs with syringes that will fit.