Django admin: search for foreign key objects rather than <select>?

My model looks like this:

class Asset(models.Model):
    serial_number = models.CharField(max_length=100, unique=True)
    asset_tag = models.CharField(max_length=100, unique=True)

class WorkOrder(models.Model):
    asset = models.ForeignKey(Asset)

Essentially, a work order is submitted and then an admin assigns an asset to the work order. The asset_tag field is a barcode that we can scan in. When editing the work order in the Django admin, by default the asset field is displayed as a <select> widget. What we want to be able to do is have a search field so that we can scan the asset tag and then search for the right asset in the DB to associate with the work order.

I know you can customize the Django admin foreign key to a hard coded query, but I can't figure out how to get it so it does a search based on a field on the admin page.