Welcome to the forum , John L .
Without really knowing what type of a wood item you have (other types of mat'ls -silk , wool , ivory , etc.) & without knowing the extent of damage to your item , it's tough to say what to do next .
If I were in your sneakers , I'd be concerned about abatement in a more general area where the affected pc. of furniture has been parked .
If it's too big of a job to take on yourself , maybe you could find a local exterminator to do it for you ?
I don't know how it works in the area where you live , John L , but here in Washington state , a bill of sale that states an item is either bought or sold in 'as-is' condition pretty much releases the seller from ANY liability in the future .
As to the PR issue you mention , proving that the 'infection' started on the retailers' premises would be problematic , esp. since you've just noticed the problem with the powder bore beetles ( it could have , for instance , came from the manufacturer , shippers , etc.) .
Perhaps a sorta win/win would be to ask for half of the abatement fee (keeping in mind that they may not have to do anything , legally) , in a friendly way , from the retailer ?
All in all , I hope you do find a method that's agreeable to you , esp. for killing those little suckers as soon as possible !