You will seldom see any chaetomorpha for sale in cartimar, you could just ask some from some folks here kung may malapit sa area ninyo.
And since most of the original chaeto batches were given out for free by some pioneer members (some even came from the states while others from batangas) I'm pretty sure libre din mabibigay sa iyo yan.
post on the chaeto thread in the macroalgae forums.
Hth