The rage in Hong Kong and slowly getting into the kits of airsoft players worldwide, Holosun optics, especially their line of red dot sights are affordable and give you more options, parallax free, more battery run time,  including one that is solar powered! Two of these Holosun Red Dot Sights are now available at Bunny Workshop.

Holosun - HS403A Parallax Free Red Dot  (Up to 50000hr Battery Life)

Holosun - HS403C Paralow Solar Power Red Dot Sight