Recommended and mentioned products
Instant remote support and remote desktop.
Normally when an agent connects to the remote client, most of the time it's with a single use password within the remote desktop app, but in this case, if I'm right, something like this is maybe what you are looking for.
RescueAssist, formerly GoToAssist, identifies, diagnoses & solves issues fast with our remote desktop support software. Learn more about RescueAssist today!
These others solutions can maybe be useful for you too : ConnectWise Control Support - LogMeIn Rescue - LogMeIn GoToAssist.