all you may need is a reasonably well regulated 6VDC power supply; perhaps even a variable output bench supply would work (set for 6 volts of course). You need to know how much current the wallwart is rated for; then the power supply should be capable of 25% to 30% more just to be conservative & reliable. Many electronics outlets such as Mouser, Allied, etc sell them. You can probably even find something on fleabay or Craigslist at a good discount.
if you can solder; look for a kit and build it yourself
if you can solder; look for a kit and build it yourself