There are only two evergreen species, Agapanthus africanus and Agapanthus praecox, but it might be difficult to find them for sale under those names. Check instead for one of the many beautiful ...

Lily of the Nile (Agapanthus praecox spp. orientalis 'Getty White ... It grows in the winter but can sometimes leaf out in the summer, with two or three straplike recurving leaves.