Since you can't match the other one (or maybe don't want to) I might look for something deliberately different, like maybe a small round one or an obviously antique style. They should be similar heights and I'd probably look for similar color, just so they don't look TOO dissimilar.

This is an inexpensive option from Target...since you don't need space for a lamp.

Doesn’t look like a lot of space, so I would do a narrow floating cabinet or shelf. Make sure the bed is actually centered between the sconces.