Licensed and documented Mammoth and walrus ivory is literally, .... ivory.
but it is pricey and fragile.
As major2 pointed out, american holly is an outstanding substitute, and economical.
I used to used paper-based "ivory micarta" when knifemeaking, and I was astounded to learn (about 5 years ago) that it hasn't
been made for ages! It was THE best stuff for knife handles and pistol grips, took stain and aged nicely, but alas it is no more.
I have been told that white-ish colored corian works well, and is supposed to take stains ( such as tea), but I haven't been able to
latch on to any.
I don't care for the look and feel of the "plastic" fake ivory grips out there.
I have tried fimo clay but it doesn't seem to bake as hard as I would like, and is "odd" to file and sand.
I have played with tagua nuts, which are excellent for very small items, but just not large enough for anything useful.
I acquired a crapload of 8x10" sheets of some sort of acrylic countertop in off-white, but it isn't taking any stain....
If I can't find a SOMETHING that penetrates I may try "burning" it gently with a powered buffing wheel...
hope this helps
prof marvel
addendum - a new search turns up these:
http://www.truivory.com/availability.htmhttp://masecraftsupply-com.3dcartstores.com/Alternative-Ivory-Sheets-12_p_2108.html4x5x 1/2 is $14 but 1/2 is as thick as they offer
and I stand corrected - I found one source for paper micarta, but I am unwilling to
drop $200 on a 1.25" x 6" x 12" chunk....
https://usaknifemaker.com/paper-ivory-paper-aged-micarta-1-25-knife-handle-material.html