English term (edited): leave-behind postcard

I agree with Asker's own suggestion, initially rejected.

It is the only solution which avoids conjuring up erroneous preconceived ideas of the style or format, while accurately conveying the right notion... and I think most people would get the idea that 'carte' would be something along the lines of 'carte postale' — i.e. of a larger format than a 'carte de visite' or a 'carte de correspondance' / 'carte-lettre'.

'Flyer', although certainly used a lot these days, to me suggests more the function, and doesn't convey quite the right idea about the form — usually a flimsier peice of paper, easier to screw up and throw away, rather than a slightly more substantial 'card' that, with any luck, the customer will keep with them a little longer.