Hard Disk Toolkit v4 will allow a live repartition, but only if you have already formatted that drive with the HDT driver.
There is no real PartitionMagic utility for the Mac today. Not from anyone. I had emailed the PartitionMagic folks about it a month ago, the reply was that they have talked about doing a Mac version but have nothing to announce.
What you can do is to email them about wanting a Mac version of PartitionMagic. The email address I used was: firstname.lastname@example.org
This is actually the tech support address for PartitionMagic, but seems like the best place to start. You do have a technical problem - PartitionMagic refuses to run on your Mac. ;)
Remember, they don't have to give us a Mac version. A nice email will do much better than "You idiots, I wanted this ****** utility months ago, I'll never buy your products again. Even though I never bought them before. You guys probably strangle babies in the spare time that you could be using to write a Mac version."
Instead, you might offer to be a beta tester for any forthcoming Mac version. And you could offer to buy a Mac version for a higher price than the average PC retail price. You could also offer large quantities of money to them personally. It wouldn't be a bribe since you are not asking them to do anything illegal. :D