If you must, clamav is the defacto standard, although it is usually used to scan emails on a Linux/BSD mailserver. The other ones I found are x86-only or android-only. You could build it locally and have cronjobs to update the definitions and scan your filesystem.
That being said, I've used Linux for about 15 years and not once have I gotten a virus or malware (one time I ran a Windows VM that got infected, but all I had to do was to roll back to a previous snapshot). While the whole marketshare point has some value, realistically the system is designed to be difficult to compromise unless a severe remotely-exploitable vulnerability is found in a process or library that is being run as a privileged user (or a regular user and a privilege escalation vulnerability is added to this).
Proper, sane firewalling if your units will be on the unwashed Internet is probably the best and easiest approach. Of course, I don't claim to know it all, and am happy to learn otherwise.
Thanks for the tip.