I agree with Wade. This is very late to have an H2S problem. Is the smell of rotten eggs, or just a rotting smell? I wonder if what you are smelling is something else besides H2S.
To test for H2S, smell your wine and remember the intensity. Put half glass of the wine in a cup with two or three clean, shinny pennies. Stir the wine for about three minutes. Smell the wine again. If it is H2S, the copper will have neutralized some of the H2S and reduced the smell enough for you to tell.
If the test indicates H2S, if you want to use copper, at most any super market you can purchase a copper mesh that is used for scrubbing pots and pans. You can sanitize it well; tie it to the end of a wine stirring spoon and stir your barrel for about 5 minutes. Then just put it in the barrel with a string tied to it to retrieve it. Leave it in for a month or so. It won't hurt you or your wine.
Next time you rack, splash rack it. You may have to repeat all this a few times.
MoreWine sells an additive - Reduless, that will eliminate H2S without all the copper and potential damage to your wine. Always leave the copper sulfate for the professionals to use; it is dangerous.