I haven't seen anything in the patch notes about these becoming more common like the Elder Charms were in 5.2 and even though the maximum amount you can carry has been increased to 20, I don't know of any way to obtain these now.
I've opened around 20 chests so far on the Timeless Isle and have killed probably 500 monsters and I have yet to see a single one of these. I read a post from a few months ago that said they are purchasable with the timeless coins but I have not found any vendor that sells them.