Fixing my bent cards

I 'displayed' my LOTR LCG box standing upright and, unfortunately, 3 cards fell down into an awkward position, bending them over the course of a week or so. They seem to have a pretty big curve in them.

While these are cards I am unlikely to ever use for deck building, it would be incredibly nice to have them out straight.

Any suggestions? At the moment, I have 'densely packed' them in between other cards in the ope of squeezing them together - but who knows if that will work.