What is a good boxed ISP

We need an ISP for programming 100 or so Mega 2560 cpus. We will have an USB interface for prototyping but burning this many devices with USB is not fun.

Something with an simple interface to pc. And easy to clone too.

Arduino ISP is probably good but we'd have to box it and make a real product of it. I need a programmer and not a kit.

So can you recommendend something, Web site or Farnell code would be good.

By the way, I first posted this on Other Hardware Development forum. In my opinion it is difficult too see for what each Arduino forum is. I mean their names are confusing