There are two alternatives for uploading routable Indonesian road maps to a Garmin device.
1. The Garmin SE Asia City Navigator has pretty good coverage of Indonesia, it seems to include a lot of small tracks that you would not expect. Asia Digital can upload it onto a Micro SD card for you at a price, I think about Rp 1m.
Asia Digital are located on the 5th floor of STC (Senayan Trade Center).
2. The second option is to down load Navigasi.net
Follow the instructions under Menu>Peta>Download
This has good road map coverage of Indonesia and you can upload the area you need through MapSource.
When you upload maps to your GPS be sure to drag across the map/maps you want uploaded to get all layers selected. If you just click on a map you only get the base selected and will miss all the roads and other information.
Navigasi.net on a Mac
The latest version of Garmin BaseCamp (and Traing Center) for Mac can read Navigasi.net but you need to convert the navigasi map to Mac format using Garmin MapConverter from Windows ( http://www8.garmin.com/support/download_details.jsp?id=3897 ) and then install using MapInstall/MapManager on the Mac.
Instructions are on the MapConverter link or here ==>Transferring Maps from PC to Mac.pdf.
The converted map is navigasi.net.gmapi and is 168.4MB for version 1.68