The recipes above will get you fairly close.
There are some oddball ingredients that really make a hot and sour soup GOOD.
The lily buds as mentioned, though usually I see more in a recipe than listed earlier.
Szechuan preserved vegetable is another. Basically a spicy pickled mustard green. Not a lot though.
For the vinegar, chinese black vinegar is best. Cook's illustrated substituted balsamic vinegar at about half the amount of black vinegar.. Not a bad substitution, but black vinegar is inexpensive and much better for this purpose.
The heat is traditionally generous amounts of white pepper, though I usually add a bit of chile garlic sauce as well. I had some the other night at a new restaurant and the abundant red chile was too much. Blazing heat. Otherwise a decent hot and sour but too much of the wrong heat.