According to http://www.upu.int/irc/en/irc_countries_list_en.pdf you're right, Indonesia does not sell IRCs.

Your best bet is to purchase stamps from the country you are sending to via the Autograph Sale/Exchange section of the forum (i.e. buy them off other members).

What should I do? I visited the central post office (since it's the biggest and I was told I could get them there), but when I went there they told me they no longer sold IRC.

I live in Jakarta, btw.

:(