I have tow ideas that both work. Maybe not within your price range, usseful anyway.
**broken link removed** This is available on ebay as well. It only allows fixed voltages and a fixed current limit. It's a nice quiet supp;y that combines an adjustible regulator ans switchable secondaries. It was really good as a battery eleiminator for a transistor radio. The wall wart was useless and too noisy.
Another think I did was to buy off of ebay a cheap DC-DC converter with current limit and voltage selection. It didn't adjust to zero and your inpur has to be 3V above the output. I mounted it in a translucent Hammond enclosure. Red enclosures for RED LEDs. 5.5/2.1 and 5.52.5 are common DC barrel connectors/ I put one of each on the box. The output was an adapt-a-plug (Radio-shack).
The idea was to have an easy way of replacing nearly any wall wart. You need a working 12 V and 24V wall wart. I needed to replace a 6V wall wart and it worked very well. Polarity changes need fidleing.
So, both worked well for fixed supples or should I use the terminology on my Hrrison Labs supply (bought by HP) Fixed voltage power supply; selectable from 0-32 V, That had a 10 A foldback current limiter. Bought broken in the 1980's for like $15.00. Repeaied for $3.00. Manual acquired only a few years ago.
It was used for a long time as a 12V fixed supply for automotive electronics. It had selectable taps.