Background - I want a Linux systems administrator who can assist me in
loading and configuring various opensource packages on a hosted server
plus providing on-going  user admin support.  I am looking for a
part-time contracter to be paid on an hourly basis.  Person would
preferable be based in Australia but could be located anywhere, but in
addition to technical skills I need good english communication
ability.  On the technical front, I need someone who can also write
script to pull together a number of open source packages such as
PLONE, KNOWLEDGE TREE, SENDMAIL, SQUIRRELMAIL into an integrated
intranet service that appears straightforward and seamless to
non-technical users, for instance a secure single sign-on.

Question - how do I find a reliable contract Linux Systems
Administrator who will work part-time on an hourly basis to support my
systems and who won't leave me in the lurch when a full-time contract
comes along.

Question - How do I find such a person

The most promising ways to get a part-time contractor who will not be
enticed away by a full-time contracts are:

1. pick someone who wants to work only part-time (e.g. for family
reasons or to continue their computing hobby and/or educational
projects)

2. pay a full-time wage for the part-time work and you'll have plenty of takers

I am guessing you mean pay the same hourly rate for part-time that
full-time employees receive, not the full-time total salary, right?

That is a good point. Too many who want part-timers think they can
thus pay a lot less per hour, and yeah, you'll lose them quick.