Apple sells the vga adapter directly or in their stores. It's the same mini-vga adapter used on the imac and ibook.
I bought my refurbished superdrive emac for $849 from the special deals tab on store.apple.com. It was specced as coming with 256 MB of RAM, but actually arrived with 512. With the addition of a 1GB DIMM from transintl.com ($199), the apple mini-vga adapter ($17), the tilt/swivel stand ($59) and a free 19" crt (work surplus), I paid perhaps $1200 in total.
For $1200 I got an effectively new (with an apple warranty) 1.25 GHz G4 system with 1.5GB ram, a superdrive, and dual monitors on a radeon 9200.
It won't outperform a G5 or a dual-G4 but it's fast enough for my needs and the bang-for-the-buck is unbeatable. (Well, for a mac. An $800 pc would run rings around it but then it'd be a PC. Like I said, the G4 is fast enough for my needs.)
-vga4life