Roof rack Ladder for GU Patrol

Wondering if anyone has manufactured/fitted a ladder to a GU Nissan Patrol rear door for easy access to a roof rack. (Not as agile as I used to be - getting up's alright, getting downs a b#@%$!).

If so, was it an "off-the-shelf" purchase (Cost?) or did you commission someone to construct it (Cost?). Not sure if the rear LHS door will cope with the weight/traffic either. I have looked at the pseudo steps that fit over the wheel but I am not real keen on carrying excess gadgets where I can get around it a better way.