While a linear will usually give a cleaner sound than most switchers, not all linear PS are created equal. The PE supply is better than the stock supply for the DUET, but there are better supplies available. The DUET also draws very little current so the inexpensive supply is not stressed.
The Parts Express PS can be used for the Touch with internal modifications, but it will be running hard and on the hot side.
The Hosfelt PS can also be used if the connector is changed, but it is on the low end of the amount of current required to run the Touch and a USB drive.
You might be able to find a used version of the power supplies I make for the SB2 and 3. They will work with the Touch.