You can find this parking lot by the Ósvör maritime museum. Small, but can be useful.
How to Find Parking lot with toilets by Ósvör
You can find this parking lot at the very end of Westfjords, pretty close to the town of Bolungarvík. If you come from Ísafjörður, then turn right after you pass through the tunnel and you are there.
GPS coordinates of parking lot with toilets by Ósvör: 66.150218, -23.215897 Take me there!
Photos of the parking lot with toilets by Ósvör: