Well, I did some searching, en even though there was a thread here on this forum with a somewhat similar request (the output had to be mirrored on a second monitor) the tool presented there has disappeared for as far as I searched

I did find a commercial tool called Ultramon that does have
mirroring and a freeze option.
Another contender in this market is Actual Multiple Monitors, that has a
mirror feature but I can't find a freeze feature there.
Also, competitor Display Fusion does have some display mirror features, but I couldn't find much info on the website, and again nothing about any freeze feature.
Maybe a feature request for AMM or DF is feasible, but there's always a 30 day trial period, and you can have Actual Multiple Monitors for 'free' using TrialPay.
(NB: No connections to Realtimesoft, Actual tools or Binary fortress here.)