Heather Neilson , The button should be replaceable. The first link below shows how to disassemble the device to access the button to change. The other 2 links may have a replacement button for you or you can also do a search using your make and model replacement buttons. If not wanting to tackle the repair pop into a good local cell/computer repair shop, have them take a look and estimate repair. Good luck. I hope this helped you out, if so let me know by pressing the helpful button.
http://www.rapidrepair.com/Merchant2/merchant.mvc?Screen=cp-kindle-dx
http://www.powerbookmedic.com/xcart1/home.php?cat=714
http://www.powerbookmedic.com/Amazon-Kindle-DX-Select-Button-p-23115.html