Username has a slash at the end

[G. G.]

One of my unfortunate users decided to put a slash at the end of his
username "username/". Is there any way to use ssh to specify that the slash
is part of the username? I've tried every combination of escape characters
that I can think of but sshd always removes the slash.

Examples:
ssh -l "username/" <ip address>
ssh "username/"@<ip address>
ssh 'username/'@<ip address>
ssh username\/@<ip address>
ssh -o User="username/" <ip address>

I've tried many more combinations, but have not had any luck. The sshd
version is 1:5.1p1-5 and upgrading is not an option.

No other remote access is allowed except for this one user, so will have to
make a field visit if I can't get it working. Thank you for your time!