Welcome to DCI! Just so you know, I removed your email address from your post, as that's usually an invitation for a tonne of spam.
Anyway, to the point - SD cards. I'd probably bet that the capacity limit for the DMC-LC70 is 2GB. There is a higher-capacity version of SD starting to gain momentum now (SDHC) that allows cards of over 2GB, but it didn't exist when that camera was in production.
The
manual (11MB pdf) for the camera is a bit vague. Skimming through it real quick, I didn't see anything that listed the maximum usable capacity of SD card. However, there is a 1GB card listed on page 118 in the accessories section, so it's a good bet that's usable anyway.
OK, here we go...Lexar sez that the LC70 can take a 2GB card:
http://www.lexar.com/2gbsd/
It looks like 2GB is a good capacity to aim at, then. That's not too shabby, especially as that size seems to be the sweet spot in terms of size/price here in the States (admittedly, I don't have a clue about how prices look down under). For example, I just ordered two Crucial 2GB cards for less than $20 apiece, which is just nuts.