Before you are thinking of replacing your rotary type shaver blades, you can try to sharpen them first. This is how you can sharpen your rotary shaver blades with a mirror and a little bit of abrasives or metal polisher. Below is a YouTube video that shows you how to do it. If you don't have a high speed internet, you can refer to the screenshots below the video.
How-to YouTube Video by Robert A. Edinger
Step by Step Screenshots
Take all the rotary blades out from the shaver head.
You can use any mirror as long as it is a flat surface mirror.
Use a little polishing paste and put it on the mirror.
Face the blade down to the mirror with the polishing paste.
Move the blade in circular motion so that the polishing paste can polish the blade which means sharpening it.
Sharpen or polish the blade till the polishing paste turned grey.
This is the comparison between the non-sharpened (left) and sharpened (right).