Try Stokes (I forget the website), they have a selection of elements for Hot Water systems. Also try Hotco (if I remember rightly). Both have websites so you can do a search for them.
Or for a cheaper alternative, find someone who repairs/replaces hot water systems. It's rarely elements that die in these things so there is literally thousands of these elements that are just thrown away, most blokes will just give them to you. Just go for the 2400W ones (alot are 3600W or 4800W-you need the circuit to run these). I've rang up several places looking for them and the blokes have been happy to hand them on to me, one bloke only wanted $5 each for them, the other said I can come out and just sift through and take what I wanted.
Finally, if you can get up to your local tip (if they will allow you to scavenge-maybe pretend your dropping something off

or just ask them, maybe they'll let you have a look through) I GUARANTEE you'll find one for nix where they dump all the white goods. Just read on the side of the cylinder for the right size element. FWIW I also found a suitable oven element to replace the one in mine that blew, saved myself $80

.
FWIW2, I have a long 2400W one that doubles back on itself that I pulled out of a HWS which is most likely going to find it's way into my kettle. HLT is already electric using normal kettle elements.
Good luck.
Justin