Most people (at least in the states) are using the trays for the classic 1020 trays. They can be purchased I believe at Transplanting Systems.
These trays are great size however they are a more flimsy plastic and won't last the years if used a lot.
Recently, people are talking about the trays from the Paper Pot transplanter as being epic. More pricey but the investment will be payed off because they just won't break. Also they have great dimensions similar to the 1020.
Mikey, Mossy Willow Farm