Does anyone know where I could get a new power supply for my 2007wfp monitor and how much I would have to spend? 

I've tried to talk to Dell but it doesn't have a service tag on it and I can't get onyone to talk to me without one.  I bought it on ebay and the seller claimed it had the warranty but because he bought it with a computer system it didn't have a service tag and thus, no warranty.  I'm an electrical engineer so I can fix it myself but I need a new power supply.