Frank Reichenbacher schreef
Is there anything to replace it of equal utility, portability, and
comprehensiveness?

+ + +
This remains as vague as it possibly can be.

If you are looking for a useful, comprehensive and portable work on current
taxonomy of vascular plants you can do what everybody else does and buy The
Plant-Book by prof D.J.Mabberley. You might recognize it as the successor of
what used to be known as Willis.

However since you give no indication on what you need it for, this might be
entirely unsuited for you.

As to equal, why not aim for something better?
PvR