well what you need to hook up a external monitor to an iBook is
1.) An iBook
2.) An external monitor
3.) adapter to plug iBook into Monitor (can't remember if iBook comes with adapter been 2 years since i had an iBook)
4.) screen doctor hack if you want to dual monitor (if you don't do this you can only do mirror)
any monitor should work that has VGA
and what is your definition of cheap (mine is the 2005FPW for 389)