The orange kit was only ever given a very limited release by the club. You can get it (without badge and sponsor logo) from any kit supplier that stocks Nike kit for about £12, same with the red and black away shirt (Lewes wear exactly the same shirt as their home shirt, Southend use the orange...
I'd like something like this, simple and effective. Would be easy for the sponsors logo to be the same style as the training gear and the goalkeepers kits and not be that massive iron on transfer it currently is.