Plexiglass

[pedalman]

I've seen plexiglass spacers on some of the enclosures (under the lid)
Does somebody make these, or are they a custom made thing?

[somnif]

Do you mean the clear plastic things? I believe those are referred to as "light plates"

[pedalman]

Yep, that's what I'm looking for

[matmosphere]

Don't they sell them over at DIY stompboxes?

[EBK]

Smallbear sells them, last I checked. 

[chromesphere]

You can of course "roll your own".  If you do, try use lexan instead of plexiglass.  Its easier to sand and less brittle.

[TGP39]

FYI:  you will need longer screws to get the lid on your enclosure.  Some sites provide them, some don't.  Smallbear has several light plate sizes for different standard enclosures. 
~Steve.