You can just snapshot the existing droplet and create a new one using that snapshot. The new droplet will be a clone of older one. :D

I an assuming that when you say that you would like to make a copy of the droplet, that you are trying to have exact copies of applications (programs), configuration files, and the data.... My first thought when i saw this question was Rsync over ssh between 2 dropleets. Rsync: is a “utility for efficiently transferring and synchronizing files across networked computers by comparing the modification times and sizes of files. It is commonly found on Unix-like operating systems. The Rs algorithm is a type of delta encoding, and is used for minimizing network usage”