A BigFix relay is exactly the solution you are looking for, just not on server hardware.
You can do this by just taking one or two systems in that place and make them relays, then all other systems should be set to use auto relay selection and they will use those machines as relays unless they can’t contact them for 10 minutes, then they will do relay re-selection and failover to a different relay.
A relay doesn’t need to be expensive hardware, particularly for 50 endpoints. It should be a desktop system with a Gigabit connection if possible that is set as a “Last Man Standing” and set to not go to sleep. Ideally it would have plenty of hard drive space for a larger relay cache and a battery backup to keep it alive durning a short power outage.
If you already have VMs running on a server in that remote location, then you could spin up a relay VM for that location.
You could also put in place an inexpensive purpose built desktop system as a relay that has no other primary function. It could be something very small and relatively inexpensive like the Dell Optiplex 3020 micro, NUC, or similar.
If you have digital signage machines that have more than enough CPU to perform their primary function, those might also be a good candidate for a relay. I would just be concerned that some of these types of machines can have very low specs and even though it being a relay won’t put much extra load on it, it might be too much.