I did one through Itsy Bitsy Bums. New diapers, cash refund, I could keep any I wanted and deduct that amount from the refund, and I could buy more diapers at a discount.
There's a thread on here somewhere with a list of all the diaper trials.
: MM Dragon's Lair (2) + trim (1) on Uruguay 3-ply
includes Green Line, RagaBabe, BBB, Joey Bunz and more.