My daughter wanted her favorite watch repaired, so I first changed the battery to get it going again.  I've never given watchbands a thought, Google research produced:
  Determine watchband end style (attachment style)
  Measure the lug ends in mm (strap size)
  Determine strap length
  Find particular material, color, style

I could have attempted to drive the streets of Oakland to find a watchband with these requirements OR look for one on Amazon. This particular watchband was reasonable & qualified for Prime.  It was delivered within 2 days by a young adventurous person (2 people in the van).