Welcome to the RXP Gold Assistant’s Guide to Disenchanting Arcanoweave Bracers.
The pattern for the Arcanoweave Bracers drops from Arcatraz Sentinels inside The Arcatraz. You also need a skill level of 275 enchanting to disenchant this item.
Note that there are five Sentinels inside the instance. The first Sentinel is after the first boss. The second and the third Sentinels are in the room near the second and third bosses, and the last two Sentinels are just before the last boss.