This is a urgent project, please bid only if you can deliver the code immediately after I award your bid.
The pop-under should have a time control to pop in the given hours, checking it either by cookie or IP.
Getting an unblockable pop-under is hard but I've seen people asking for it here, so I guess with your knowledge you might do it.
3 freelancers are bidding on average $100 for this job
I've already done this before & is ready to show you demo. Please let me know If I can take the opportunity further. You can award me the project after demo. Thanks Vikas Choudhary