A friend helped me make a few covers and they came out VERY well for a real cheap price. I documented the process and put together a video for those who want to make their own. Hopefully it'll give you some ideas.
<iframe width="560" height="315" src="https://www.youtube.com/embed/n8pZlWZ4Ttc" frameborder="0" allow="autoplay; encrypted-media"></iframe>
DIY dust cover for keyboards/synths and even mixers/consoles
Moderators: Sharp, X-Trade, Pepperpotty, karmathanever
And making covers for Studio Monitors:
<iframe width="560" height="315" src="https://www.youtube.com/embed/4C9oOdku7rE" frameborder="0" allow="autoplay; encrypted-media"></iframe>
<iframe width="560" height="315" src="https://www.youtube.com/embed/4C9oOdku7rE" frameborder="0" allow="autoplay; encrypted-media"></iframe>