How to farm 500+ 'Grand Black Scythe Artifact' ?

Tujen wants to haggle a mirror shard for 800 'Grand Black Scythe Artifact'.

I have 70 at the moment.

It seems artifacts can not be traded for.

Any tips on how to farm 500 additional efficiently?
(and is it even worth it?)

Buy logbooks with "Black Scythe Mercenaries", and run them. It shouldn't be that much of an investment, 800 should be easily achievable.

Thank you for the help.

Been farming +200 now, went to check Tujens window ... and it has been rerolled... I'm bloody screaming inside now.

Edit: Oh wait!!! I didn't realise that different characters had different trades from the Expedition-NPCs. It's still there! :D

Edit 2: I have bought it now. Wasn't painful at all to farm. Thanks again for the help.