I've written some about a DIY silver salt treatment. Sort of like Polygiene concept.
Take a 9 volt battery, wrap some silver wire around the positive electrode. Put some copper wire to the negative terminal.
Take some distilled water, mix in some of the purest sodium chloride you can find.
Suspend battery over glass container or glass with the two wires going in the water (the wires must not touch, but be evenly spaced apart). Keep away from heat and light exposure–these can create chlorine gas, which is toxic (so do in a well ventilated area). The silver will start to replace the sodium, and you will get silver chloride. Time depends on how much water, and water salt ratio you use. With a fresh 9 volt battery, a few hours should be sufficient as adding salt speeds up the process of electrolysis over straight distilled water to make colloidal silver.
Then, make sure your shirts are washed extremely well, hot water, strong detergents, and very well rinsed. Get some dye removal stuff. Follow direction to remove some dye, again make sure to rinse very well.
Get some I Dye Poly of color you want. Follow directions of boiling water. Your silver chloride water will be your main water to add to the mix.
The idea is that as the dye bonds to the surface of the fiber substrate, it will bond the silver chloride particles and ions with same.
How did i figure out this process? A combo of reading Polygiene's literature, about how they use very little silver, to make their silver salt for their treatment. This immediately clued me into a electrolysis process, as i was previously familiar with same from experimenting with making so called colloidal silver (usually actually silver oxide, which can be reduced to true colloidal silver with some further chemical transformations). This, also uses very little silver. One wire will last a very long time, many treatments.
As mentioned, they specified silver chloride, so basically i knew you just had to add some salt for chloride to get the silver chloride rather than the silver oxide which is typical of the beginning colloidal silver making process.
But the biggest clue, was during talking to Polygiene about something else, and they let me know that their professional, manufacturer treatment of silver salt, the so called "permanent" treatment that companies like Patagonia use, is added during the dyeing process.
This obviously is what bonded the silver salt to the synthetic fiber substrate (the exact mechanics i'm not sure of). However, i am not certain that a home dyeing process is similar to the type manufacturer's use, or that they don't add something special to help it bond better with the dye.
The biggest initial investment is the silver wire, but since it will last a long time and for many treatments, not a big deal. Everything else is cheap. Anyways, i've treated a few items, and tested one shirt. The dyeing job wasn't perfect (shirt was previously white, and i used yellow and some areas were a bit lighter or darker than others), but it did seem to have some anti-microbial/stink properties after. It's an all polyester wicking shirt with no previous antimicrobial treatments.
It's probably not as good as the manufacturer Polygiene process and treatment, but better than nothing.