I created this for myself and thought I'd share it here for others to use if they wish to have it. This casing is specially made for yuvalaj's One Blade Tray has created. 

This is the link to the tray

https://makerworld.com/en/models/113362?from=search#profileId-159728

The housing perfectly holds in the tray under the slider allowing enough room for the trimmer and it's accessories to fit inside and has a cap style latch for the opening. Note that the tray goes in only one way so if it looks like it's not going in try flipping it and sliding it in the other side. Hope you find this useful!

I've noticed the cap is having trouble sticking on at times after the first few days, I'll try to redesign the cap; you're all free to edit the design if you wish the stl file is available to download.