I use Kugler's Silver Blue. Maybe it would work for you, comes in rod, powders, and lots of frit sizes. I don't know of a clear silver glass, that would be something to play with if it was produced. Kugler also makes a Silver green & silver purple. Also, they (Kugler) make a lead crystal that I've seen on the selves at SPB, I don't have any idea if it will reduce. You might want to talk to whoever you buy color from what they'd recommend, they can often be very helpful if you happen to get the "right" person on the phone.
You mention silver nitrate in liquid form. I've never seen it as a liquid, but assume you'd spray it as with other "fuming" solutions. The silver nitrate I have seen was in solid form, which could be crushed to make a powder. Or could be used as a solid, holding with tweezers you could draw with it onto the hot glass surface.
Can't remember exactly how to make it.....I think you just pour nitric acid over pure silver (must be pure, not sterling), which dissolves the silver, then let the acid evaporate. I can't remember the "details", maybe you rinse away the acid or "something".