[V6-12v] broken bleed screw for hwater hose

[Clive Young]

As things usually go for me I have once again succeeded in making a minor inconveinience a major breakdown. I was trying to bleed air out of my heater ore after flushing it . ( for those of you unfamiliar I am trying to fix a no heat condition in the car.  ) . Anyway sure enough I broke the bleed screw. I have heard this is NOT available seperately from the dealer but I did hear of someone either finding a supplier or substituting it with something ! It is basicaly a 10mm plastic screw !  Anyone have any ideas before I head off to home depot plumbing dept ?