Currently the only way to obtain Riven Transmuters is to hunt Eidlons. I've hunted several back in my day with over 500 tricaps, which isn't really that impressive. I've recently have used up all of my riven transmuters and would like another way for the community as a whole to be able to obtain these outside of eildon hunting.
You can add the to Teshin as a weekly or daily with a limit obtained via Steel Essence. Add to the Sortie and Archon Hunt reward pool, Add as a drop in Steel Path loot rewards and even in abriation. Even on the Arbiters of Hexis Vendor for Vitus Essence. If you really want to push the envelope you can make them purchasable in the in game market for 20p each.
At least give it a thought about having it obtainable by some other means outside of hunting. Thank You