If what we have today is a market econmy, then a market economy is perfectly acceptable way to address the issue: taxes of some sort.
clearly there's more to it than that, but assuming that the market can address any negative externalities just with taxes is pretty naive IMO
Edit: W.r.t. regressive taxation... No one has the right to force their externalities on someone else. Just because you are poor doesn't mean you can dump your garbage on my lawn because it's cheaper than paying to haul it to the dump.
For this reason, if the tax is regressive, its perfectly OK for the revenue to be redistributed in tax breaks to lower income.
Affected Company B changes their packaging, e.g. to recycled paper, to avoid the tax at a 0.1% cost increase and passes it to the consumer.
You tell me what happens next.