It's certainly possible that the methoxy group in DXM could be replaced with a sulfoxy group, but it would require some extensive chemistry knowledge to synthesize such a chemical and not something for the lay man. If a sulfonated version of DXM existed and was worth making, big pharma would likely have already had it on the market.
Quote:Maybe I could indulge responsibly once in awhile if there was some more potent form...
Unfortunately, it seems your only alternatives would be to increase the time period between dosing so your tolerance can drop or find a safe potentiator of DXM.