I don't know if this will help, but here's what I do when fly fishing in S/E Alaska, which means we have A LOT of saltwater, water, and well, more water.
I carry a 329PD in .44 Mag in a nylon chest holster. Nothing fancy. My gun gets wet, quite a bit, with both salt and fresh water. It's my back-up to a shot gun.
S/E Alaska is a rain forest, so keeping anything dry is nearly impossible. After several trips, both my 329 and my "Robarized" 870 do not show any signs of rust - at all.
While in remote areas of AK, both are wiped down when I can, but by no means are they given a proper cleaning. My point in this diatribe is that the material of the firearm and cartridges is more important than the material of the holster.
PM me if you need more details on keeping them functioning in an environment that's pretty hostile to, well, everything.
I hope this helps.
Take care,
DFW1911