What you would need to do is approach Jw`s individually by whatever means you find to identify them .As pointed out the organisation will be no help to you here,
And I wouldnt hold my breath in thinking you are going to make a killing or even enough to put food on the table selling life insurance to a JW.
No bona fide JW is going to buy life insurance , no way .Armageddon is always just around the corner so no need for life insurance.
In fact being a JW is in itself life insurance ,this system cant last more than 5 years ,why do I need life insurance ?
If I happen to die I will be resurrected ,why do I need life insurance.?
You obviously have little or no knowledge of the beliefs of Jehovahs Witnesses.
Do yourself a favour and look elsewhere because you will have no success their.
Good luck with your career.