That's so cool, I used to love 'em as a kid, they were pretty popular here in Italy during the late '80s/early '90s.
I'd like to give 'em a try again, maybe while in bed just before falling asleep :-D
What's the cheapest solution to have a go at it and bring back once again such good memories?
I always chose to avoid those R4 things just so to completely avoid the temptations of the 'ole AHRRRR... if you know what I mean.