Andrew, you'll find the GSO Superviews at Andrews Communications. Look under the GSO heading in this link"
Andrews Communications
The best price for a new TMB Planetary I've seen is here in Oz too. The two I've mentioned are available:
VIT Optics Australia
The TMB's do occasionally also show up in the classifieds section.
There are much more expensive eyepieces, and better quality (though it is hard to beat the TMB's for their image quality) and wider field of view, but these will perform exceptionally well for you. They also retain their value very well when you want to sell them on.