Well, thanks to reader's comments, I think I've found a good solution to my seed trays. Thanks for doing all the heavy lifting for me folks! Look what I found...
According to Charley's Greenhouse, it's 12"W x 17-1/2"L x 2"H. That way I can fit four of these under my four foot light system. Then, if I someday get the 2" soil block maker, it should hold five or six across. Not sure if I need to get an insert try to keep the seedlings off the bottom of the tray, but this will keep the water off the board and out of the room, hehe. At $10 each though, this seed starting system is getting more and more costly as I go through. Silly me for not planning better. What was I thinking? Hehe.
I didn't see anything like this at Lowes, so I guess a trip to Sky or Emery's is in order. Tomorrow's plans just got changed, so I hope to rush out and get some work done in the yard before I have to help my folks.
Hope your weekend is going swimmingly!