They're cheap if you just buy an appropriate PSU. You don't need an actual brand one. The brand ones are probably a worse idea than buying a brand new one at this point. I had my SGX and Duo R bricks both die on me recently.
Check the amperage, polarity, and connector, and get the same thing. Those adaptaplug ones that switch between like 5-12v are the best bet. Just don't buy a piece of shit one. You should be able to find a solid one for like 15$.
If it's like 2.99$, pass.
I had one from Radio Shack. I sold it when I sold my Duo-R. I used it with the Duo-R for about 6 years, including leaving it running for 8+ hours at conventions, or when I would leave it paused to go to work.
It was like 7.5-12v 1000ma, and cost maybe 12$