I ordered one for $16.80 and it works like a charm.
The story, to make sure I don't mislead anybody unintentionally:
I bought an L1 as part of a tank breakdown package. Turns out that I didn't get the power adapter. I then bought a new MP40. A few weeks later, an old mag24 return pump failed, so I wanted to put the L1 in its place. I borrowed the adapter off of the MP40 and put it on the L1. It worked well, so I wanted to find another cord so I could use both pumps.
Therefore, I can't really say that this power adapter is exactly what comes with the L1 pump. I just know I've run it for about a week and a half without any problems at all. I'm pumping up about 11ft and it puts out enough that I can't run it wide open or the overflow begins getting pretty noisy.
Here is the part I bought:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1