looking for a double sided scanner without rollers

[ijustdontknow]

I know hardly anything about scanners or what you call them or the proper names. I am looking for a double sided scanner without rollers. In other words you press scan and it scans the top and the back at once and saves it as two files. I seen expensive scanners like fro 5,000 do this. but is there is anything cheaper?

if it helps any I am scanning postcards and do not want to wreck them with the rollers.