Key fob detection failure can be corrected by replacing the battery in your remote. If that doesn't do the trick, here is a technical paper to assist you.
This is a comprehensive overview of the different approaches to conceal the Spotlight hole in a Police Tahoe.
On-line search tools designed for civilian normal production vehicles can be a challenge when looking for parts for police vehicles for several reasons. This article from Nenno Products LLC provides some strategies to look between the listings to identify police built vehicles in databases that often times fall short of what would normally be an easy task look up and where to search for them.
Removing the spotlight leaves a large hole in the A pillar of the Explorer PI Utility. Aside from spending tons of money at your favorite body shop, here is a solution you can do yourself and quickly.