You need a Scandoubler/Flickerfixer that will double the output frequency of your Amiga.
Some are external, some internal.
The best is the internal ICD Flicker Free Video 2, followed by the Multivision 500.
They pop up occassionally on eBay for about 50-75 $, a bit cheaper if you speak german, there is a nig market in germany for Amiga things.
It is roughly as big as the market ebay.com offers, which is including the UK and Australia if you make a search for "Amiga" and filter out the Amiga things.
Have fun,
McTrinsic
