You can buy air tickets online for Batavia (Sriwijaya too)

[Seekup]

Just FYI, I used the ticketIndonesia.info site, worked fine. After a few days they sent confirmation. I used it to book lion air because it wasn't taking my us credit card.

I used them to book a Merpati flight for July 2013. Their site is easy to use and their emails were prompt. The commission was approx $55 for a $270 ticket. I doubled checked the confirmation number with Merpati and all looks good.

 

[puncho]

That's a pretty high commission...mine was about $5 usd for my makassar to Lombok flight.