I buy the blue teflon insulated Neotech solid core OCC silver from Sonic Craft in either 28g or 30g. I also buy UP-OCC bare solid core silver from a popular e-bay seller claimed to be sourced from Neotech. I have pulled the Sonic Craft Neotech sourced OCC out of the teflon jacket to compare to the e-bay wire. Both look identical, possessing an absolute flawless polished "blue" diamond like reflective finish to the wire surface.
Also buy bulk OCC copper from parts connexion, and that stuff needs to be polished out by hand drawing thru your fingers. Off the spool is rather "rough" and unrefined in surface appearance. Have not tried their bulk occ copper.
For a cheap source of stranded OCC copper wire. I take apart Outlaw Audio PCA cables which contain 4X 20g polyethylene insulated wires. Can be used to great success in making power cords and DIY interconnects.
I have found solid core OCC silver wire to have an identifiable sonic character. Prefer to use smaller guages (28-30) as the larger guages exhibit too much coloration for my taste. Midrange is fully fleshed out with tonal color similar to copper wire. Bass is full, deep and powerful. The highs are never bright, harsh or spotlit as can be the case with other silver wires. Yet it possess the resolution of inner detail one typically only hears from silver wire.