Is there an weapon (item) which increase your power roll like "Power Well" ?

I got a force sword from the enemy psyker in the second part of the harloc triology, but tbh i dont really use or even need it.

Ravenor got his chair, i want my staff or sword ;-)

Such an item dont have to be easy to get or be cheap. I just want an goal.

Eldar are known to be masters of Psy-Tech. Surely the Eldar have such devices and weapons? So logic says that I should seek out such devices. What could possibly go wrong?

If I remember my Ravenor, he was sitting on a big chunk of Wraithbone that amplified his power and his ship had several pillars of wraithbone that he would link into for even more power. All of his operatives wore wraithbone pendants that allowed him to track them more easily.

So make some wraithbone magic necklace that gives a bonus to activation, range, duration, damage, or even a penalty to a targets opposed check.

You could also put this kind of bonus into a weapon but most psykers would probably prefer more subtle things.

One option would be to force a quest on your psyker to craft an item that would act as a power well.