Hi SamL,
I've been using the Harbuch Electronics transformers with success. They make them on the premises at Hornsby and have hundreds, if not thousands in stock. I've never had much trouble getting wierd voltages such as 22V and 28V etc.
Very good prices as well, try for a discount, I was successful for my first 4.
If you decide to go with them,I live local to them so if I can help, let me know.