Need help rigging a sword to a hand for blender

Like the title says, I’m looking for someone to help me figuring out how to rig a weapon to an R15 model.
As a blender animator when I animate the R15 rig and import it to the studio, only the body’s animations can transfer… I’m looking for a way to sort of weld the weapon to the character in a way that lets me move the weapon in blender and import the final animation with the weapon already animated onto the rig if it makes sense.

Having the same issue except I’m using the default animation editor, have you found any solutions?