@Bacpacker couple of suggestions...use a humidifier or vaporizer at night or as soon as you get home to have it running while you are at home. Elderberry is a good suggestion but if you can find these other herbs in tea form or in a tincture to add to the tea, or even in powder form, you can make tea and add tincture or powder to the tea.
I don't get sick much with long term coughs anymore. When I did, I would make tea out of these herbs I'd get at the health food store, etc. or online: red raspberry leaf, mullein, slippery elm, marshmallow root, pleurisy root. It worked, or I wouldn't have suggested it. Drink a lot of it, as warm as you can stand it, with honey, lemon if you like. Usually can only find slippery elm in powder form and it doesn't take much.
Just drinking red raspberry leaf tea by itself is good too, add honey. It actually tastes like regular tea.
Barring all of that crazy herbal hippie talk, most grocery stores carry yogi brand or traditional medicinals brand of teas for coughs, etc. and they work pretty well too. Yogi has Breathe Deep and Traditional Medicinals has Breathe Easy, Echinacea Plus Elderberry, and Gypsy Cold Care.
Does your wife use essential oils and a diffuser? I use these oils mixed together in a diffuser when sick with sinus or respiratory issues: peppermint, geranium, rosemary. Some people put oils in their vaporizers or humidifiers. I think that's a bad idea as the oils are hard to clean from whatever you're using to disperse them into the air. Using a diffuser is better and you may be able to find one at a drug store. Of course, there's always Amazon.