Pens are thermoplastic, gently heat the tip over a naked flame, then squeeze it together. Beware of the airhole half way up the thing... not so easy to plug that one...
Florists also use a transparent plastic testtube often to stick the flowers in... perhas you could check there' I'm sure they wouldn't charge you a dollar.
the other thing you could try would be a section of TV aerial. you don't actually need to see through the thing, you could mark the gradations on the outside.
Florists also use a transparent plastic testtube often to stick the flowers in... perhas you could check there' I'm sure they wouldn't charge you a dollar.
the other thing you could try would be a section of TV aerial. you don't actually need to see through the thing, you could mark the gradations on the outside.