You can buy ANY scandoubler or scandoibler/flickerfixer that connects to the Amiga's external RGB port. Thos will also work in any Amiga model.
There are some internal ones for AGA amigas that connect directly to the chipset to get the digital video signal but I don't know if there were any equivalents for older Amigas.
In your case I'd personally choose the first ones becase like I said, they'll work on any Amiga.
