This is really horrific. But as this was second hand I'm not sure how having "independent third-party certification" in place would help, unless you could either get something you bought certified afterwards, or it was illegal to sell secondhand without said certification documents (but then you still run the risk of forgeries or after purchase alterations).
It points towards a bigger problem to me, that of dodgy imports in the first place. We need
Online market places to be jointly and severally liable for anything on their sites. No more shirking responsibility by saying it's on their sellers.
Proper import checks (thanks Brexit) to catch stuff that's not up to the existing safety standards.
More money put into enforcing existing safety standards in general
To work closely with the Chinese government to tackle dangerous products before they're out on the open market.