I do not think that there is a way to limit what someone can view in the syslog. To verify, I checked the Manage Accounts page as well as the Manage Views sections. Unfortunately, neither of these offer the option to filter syslog viewing.
I guess the only thing you could perhaps is tosetup rules on your SolarWinds/Orion server to forward syslog messages from specific nodes to a different syslog engine. Better yet, if you have access to those switches, routers, etc., you could configure these to send syslog messages to the Kiwi Syslog server in addtion to your SolarWinds/Orion server. This would avoid load on your Orion server, which is always a plus in my book. Having the syslog alerts sent directly to the Kiwi syslog server would also make it less complicated to troubleshoot -- if your Kiwi Syslog server stops receiving syslog alerts (for example).
As for which other syslog engine to use, Kiwi Syslog engine comes to mind.If there are 5 or less devices, you could use the free version of Kiwi Syslog engine. Or you could buy the paid version, which allows for unlimited devices -- it is very inexpensive. Once you install and configure the Kiwi Syslog server, you would point your client to the Kiwi Syslog website. I think that would work quite well, but as you can tell it does require more effort than just limiting views.
I hope this helps.