Look at Juniperus chinensis/Chinese Juniper.
There is one called 'Spartan' which should stay narrow as it grows, but as they say "your mileage may vary".
Are the trees being planted for privacy? Since the space is so narrow have you considered adding a decorative fence on top of the low wall and planting some type of vine which will hug the wall and the fence? This link has some suggestions for evergreen vines in your area.
https://www.wildflower.org/exp...
One more question please. Have you talked the neighbor with whom you share the property line? They may have some suggestions as to what might work and please both parties.
