I wish I had a good answer for you, but I machined my own mount and used a Sinclair port level loading block with a flexible arm for the ammo, and my cell phone as a timer. You might contact seb and see if he has any contacts or has made one himself .
I do not have one mounted on my rest, but bought a few of these in different caliber set ups, from a guy on AccurateShooter.com. They work well for me.