The ISO images are available here:
Milestone m30, standard image
Milestone m30, minimal image
Milestone m29, standard image
Milestone m29, minimal image
The m26 ISO for SPARC is far more stable and supportable than previous ISO images, but do check the Release Notes before proceeding.
You don't need to download the ISO, you can run Tribblix in the cloud.
Some older images are also available.