The dark purple plants are Phomium tenax "Atropurpurem".

Would Home Depot or Lowes carry this plant? Is there another for this plant?

Home Depot carries Cordyline(Red Star) which has a similar color and look. I haven't seen New Zealand Flax(Phormium tenax) at Home Depot.

I only found Phormium 'Jack Spratt' (Dwarf New Zealand Flax) at Home Depot. I also saw Cordyline, as Lang Pools mentioned. I would check with your local nurseries. They usually have great selections. I would be careful planting Cordyline, if you don't want the trunk.

Jack Spratt are no good in heavy soils. I think you'll find these are Phormium cookianum (NZ Mountain flax) and do best in drier conditions and lighter soils. The Phormium tenax (NZ Swamp flax) is a far larger variety and prefers moister conditions to it's mountain cousin. The tenax can reach 2.5 meters high and then has taller flower spikes above that, the cookianum generally stays below 1.2m and smaller, so is a better choice for urban gardens. Just watch for mealy bug or scale.
Cordyline is a tree and shouldn't be confused with Phormium, quite different species, however Cordyline and P. tenax like similar conditions are are very hardy to airborne salt, wind and naturally occur in lowland, estuarine and coastal dune swamps. Our Cordyline are suffering and dying out randomly and quickly in NZ due to a bacterial infection (pytoplasma) transmitted by the Australian passion vine hopper, so plant them please, they so cool and make a great noise in the wind!
Check out "Dancing Leaves" by Philip Simpson ISNB:0908812760