Dock comes in two different type of power supplies =  HG5D1 130W Liteon AC power adapter47RW6 180W Liteon AC power adapter You can find yours from invoice. If you do not have invoice you can go HERE and enter the service tag of your dock to find it. You are looking for this.  
Hi, I have a Dell Dock WD19S. Sadly, I have lost the HG5D1 AC power adapter. There seem to be similar items on eBay, but would anyone know what substitute I should be looking for, ie power and type of socket? Regards
WD19S, lost AC power adapter