Went to a yard sale a few days ago and found two vintage dental syringes (sans needles of course) it was as as easy as drilling out the part where the needle goes and adding a cartridge from a pen. unsettling looking hunh?

all in all it set me back 50 cents. I would do more but I don't have enough syringes and I can't do commissions. but I will say this this was easy as pie.