I am building a home that has planter boxes integrated into the eaves. These planter boxes are accessible from slider windows in the home. From the exterior, the planter boxes take on their own box shape and measure about 30" high, 24" deep and anywhere from 8 to 14 feet long.

I'm looking to wrap the planter boxes with light-colored wood strips (horizontally) to create that very modern look. But because of accessibility issues, I am leaning towards an "alternative wood" like Trex or similar. However, Trex is for decking and they don't seem to have strips that are cut to 3 to 4" in width (6" planks wrapped around the planter boxes won't look very modern). In addition, I'm looking for strips that have slightly different colors so they can contrast each other.

Can anyone recommend a reliable, low maintenance product that can be installed over these planter boxes? Thanks in advance!