You might want to look around here first before posting stuff thats already been discussed MANY times over many years. The LM317 is nothing new to all of us and many here use it.
The problem with the LM317 in the TO-220 package is that the stated minimum quiescent current (which in a current limiter must flow through the load) is about 10ma. You <might> be able to get it 20-30% lower due to process spread but its not getting down much farther.
A better solution I've talked about many times is the LM317LZ in the TO-92 package. It has a maximum output current of 100ma BUT it has a quiescent current around 2ma maximum which puts this variant of the regulator squarely in the adjustability range we want for Colloidal Silver production. I don't know anyone here who runs as low as about 2ma but some guys make cold and do run 3ma. Its also cheap as dirt from China. Though prices have gone up some more recently, I bought 20 of them a while ago for less than $1 (thats for 20 of them!)
For a power supply even an old laptop charger works. Most are 19.3V which is plenty. This is what I currently use.
The LM317's headroom is 2.5-3V meaning VIn must be 2.5-3V higher than maximum VOut of the regulator itself. Given we set our cell to 10-12V, even 15V works with the LM317 (but barely). 19.3V is plenty, usually.
The 2 transistor limiter as an alternative, has a headroom maybe around a volt so with this, for sure an old 15V laptop supply works.
There are many other solutions MUCH smaller than using a power supply or laptop supply and no, unless you're making bathtubs full of Colloidal Silver, you don't need 30V.
You can buy tiny boost converter modules from China (adjustable from 2-28V) which have also been discussed here a few times before over the years and a few guys are actually going this route, for less than 50 cents each, and you can get them with a micro USB power in jack so a $1 cost from dollar tree wall plug cell phone charger (5V, 1 amp) if even you don't already have one you can use which most of us have a drawer full of cell phone chargers already, which is TINY, is all you need beyond the boost converter, USB cable and your limiter. That'd all fit in a box about the size of a pack of cigarettes if even that big. That boost converter can put out 2 amps so even if you set it to the maximum 28V, given the chip on the thing is 90% efficient, with 1 amp input (what most standard wall chargers can supply), you'd be able to supply about 160ma to the cell. Normal use isn't even close to this.
Start simple and only make something more complex if simple isn't doing it for you (wink).