If lost after the quest, a new one may be obtained from Sir Rebrum, who can be found north-east of Rimmington, by the mine in front of the Queen Black Dragon's Lair. Sir Rebrum can also be found by using the teleport option on Remora's necklace. However, a new one cannot be obtained if the player owns a royal crossbow (having an augmented royal crossbow allows for the player to reclaim the coral crossbow).
This process requires 70 Smithing, and the new crossbow requires 80 Ranged. The crossbow can be completed by exposing it to the Queen Black Dragon's fire attack during her final phase, which requires 60 Summoning, creating a royal crossbow.