Thanks for the update. those don't look like top hat grommets. Are they grommets used in electronic panels?
They're "push in grommets" that I bought from McMasterCarr.
Edit - McMasterCarr is one of my favorite online supply stores. That's where I purchased the water solenoids that control my reservoir auto topper. I like to give plugs to business that deliver. Their specality is electrical supplies. I've purchased float valves, sewer pipe end caps, thermostats, and grommets from them.
I found an online dealer for irrigation supplies, irrigation direct, that has everything to do with irrigation. They sold me the 1/4" 90 degree barbed elbow fittings for my drip lines for super cheap.
http://www.irrigationdirect.com/irr...p-irrigation?gclid=COHEtd7RzKoCFUFo4Aod0lfBzw