We recently ordered some heavy duty 10x20 seed trays in a lovely blue color from Bootstrap Farmer. 10 trays for about $72, including shipping and tax. They should last us for years.

I think they mainly sell to nurseries, but I have to say I was very impressed with both the merchandise and the way it was packed for shipping.

These are slightly smaller than the 10x20 trays we have from other sources, which is a good thing for us because they fit better on the shelving unit I've got the grow lights on.

I'm studying their website to see what else they have I might want. The other 10x10s we have don't quite fit in the 10x20s, so I'm thinking I may order some of their 10x10s with drain holes.