Sonic screwdriver lens?

[Galifreyscall]

I've been modeling my own RTD era sonic, and I've hit a roadblock at the lens. Are they an off the shelf part, or are they custom cast? I've seen some makers use lenses like this:

but they seem to be way too tall compared to the onscreen prop. Nothing I've ever found has compared to the two aztecs, which leads me to believe that it was made in house. If so, how are they made?
Many thanks y'all!

 

[JPH]

Find a screw with thread size you need, sculpt the blue lens on top of it (threads up). Cover in release agent. Make a mold out of rubber or silicone then cast in clear resin, color matched with appropriate pigment.

 

[Galifreyscall]

Find a screw with thread size you need, sculpt the blue lens on top of it (threads up). Cover in release agent. Make a mold out of rubber or silicone then cast in clear resin, color matched with appropriate pigment.

Thank you! I was planning on modifying a lens like the one I previously posted and casting that, or modeling one and 3d printing it in a transparent blue resin. I'm building one for myself, and one for a local convention's charity art show, so since I wont be mass producing them I can put a decent amount of time handmaking them if need be.