After some playing with fitting the prototype into various containers to provide suitable light diffusion and deciding the re-purpose a sun-in-a-jar which has the requisite frosted surface I looked online for a source of frosted jars / containers.

It seems that the best source is the aforementioned sun-in-a-jar, but another option presented itself in the form of frosted glass spray.

Some more mulling later and the Ball brand mason jars (screw lids with separate top disc) could provide a low cost ubiquitous housing.

I did a layout in eagle to make a disc PCB to fit the control screen, encoder and processor into a 5cm x 5cm area.

After pulling together some models off grabcad I came up with the following design;

I need to get the prototype working with the new screen and still to get the ATMega asynchronous clock working using a watch crystal, but it looks like should be possible to put together a pretty polished version at the end of it.