MMP sabots probably makes the Super Glide sabots for TC.
They offer 3 diameters with their own label:
HPH12 - .507 -.508
HPH24 - .505 -.506
3Petal-EZ - .502 - .504
The main alternative are the Harvester Crush Rib sabots which the maker doesn't list the diameter of, but which are known to be easier to load.