The only 'NOS' things I come across seem to be for Dreamcast, which is definitely 'retro'
I've never even seen a new amiga game before :/
I do a lot of shopping for 'retro' (megadrive, dreamcast) sort of games, but I refuse to ever buy 'NEW' as in sealed games. I buy my games to play, and it feels a shame to unwrap factory sealed games when there's perfectly good used copies for the same price.
I suppose the closest I could come is I managed to obtain a NOS control panel overlay from 1989 for my Sega Megatech arcade machine.