Timings for the Wandering Sidhe:
To specify which gear slot you would like to purchase the Neverwhen for sayto emp prefer <type>. Preferring decreases the quality by approximately half, so you'll have to give double the gold to get the same quality. The maximum amount of gold that you can ever give him per item is still capped at 500,000 gold, however since the quality is halved you will have an item that is actually of the "250,000 gold" grade, and the amount of gold registered under your name (for the mark) is also capped at 500,000, so even if you give 1,000,000 gold, it will still register as only 500,000 gold for that instance.
If you do not prefer you will need to give 500,000 gold for a top spec item with no negative attributes.
If you prefer you will need to give 500,000 gold for an item of equal value of 250,000 gold without preferring.
Neverwhen equipment can be repaired by the vacationing blacksmith in the Wandering Sidhe. Have 100,000 gold in your inventory and give him the item you would like repaired, he will take the gold and give you the Neverwhen item back fully repaired.
In addition to buying Neverwhen you can also give a non-existent payroll stub to the employee in exchange for a good quality item. The stubs can be obtained via winning the lottery as a bonus and as one of the generic boss loot items.