Here are the white trays: Amazon.com: Cubette Mini Ice Cube Trays: Kitchen & Dining
I bought these too but I haven't tried them with making fish food yet: Casabella Silicone Mini Cube Ice Cube Tray, Set Of 2: Amazon.com: Kitchen & Dining
Found a great deal on the mini ice trays and shipping didn't seem that bad. Set of 2 Miniature Ice Cube Trays 1244/2. They are like the ones you show in the first link.