So I've tried replacemet grommets from Lowe's and Ace and neither one worked well for me (grommet would push through or not lock tight enough). I was in O'Reilly's today and saw this by the Vacuum Tee section.
It's a nice tight fit and doesn't look like it'll go anywhere. BTW, couldn't find a 4 way 3/16 tee (they only had 3 way). Know anywhere else to look?