A good bottle of some Vit D3 ... and some good Vit C will serve much better then any drug.
I also keep Garlic, Echinachea, Olive leaf, Elderberry... and a few others around at all times.
Personally I would drop that Thera-Flu it just has too many risks for me.
I also keep a variety of teas, mostly formulated for colds & respiratory issues, as well as chamomile and peppermint.
As for electrolytes, some good unrefined salt (such as Celtic salt) is what I use for that.
Distilled (white) vinegar will clean as well as any "disinfectant spray" and is totally safe to have around (as well as cheaper).
Don't really have a "kit" just for flu, but would take large doses of the Vit D3 and treat symptoms. Up to 10,000 units per day will kill off ANY flu much better then any drug on the market. It can also be used (at 2,000-5,000 units per day) as prevention. Its fairly cheap, and your body needs it for many functions.
~R