Never heard of a Junker blaster, but there are however many Blade Runner replicas, I had the luck to see (one of) the actual ones used on the set of the movie, displayed in the Planet Hollywood in New York
There was no Blaster replica as far as I know. You're probably thinking of the Hyper Blaster, Konami's pre-GunCon light gun for the PlayStation. It was featured in the original Silent Hill.