here in adelaide Sleeka Spares could get them in for about $120 for the smaller guides and almost $170 for the curved top guide i think? they are very costly, just be prepared to cough up if you want new ones.
found http://www.swmotorsport.com.au/
who can get them, and have an online catalogue with approx prices. they are NSW based so may be easier for u to reach. not sure if they stock the bottom-chain guides, but they were helpful over the phone when i needed inlet valves and seemed to know what they were doing. These needed to be imported from Japan, but they were only $13 each or soemthing which i was happy about!
i seem to remember posting this addres a few times before on the topic of timing gear/18RG/2TG parts... i dont wana be putting toymods sponsers out of the picture or anything but its just who i found when i needed rare bits, and i know what it feels like to have an old engine..