Jep, Jay is right. I used ribbed styrene from Evergreen. The accurate part # is 4529.
1. Were the electronics part of a kit or did you build it from scratch?
I bought the electronics as a finished kit online from a big electronics retailer here in Germany, but then modded everything about it except the chip with the circuit on it. Everything else (LEDs, battery holder, trigger switch) was replaced according to my needs.
3. After such a clean build with the styrene, is there an advantage (besides multiple copies) to casting it in resin?
Hmm, i guess not. :angel I think the electronics could have also easily been installed into the styrene build, so no advantage there. However, casting in resin is the method that is (or was) primarily used during the production of the show, so in terms of accuracy, that's IMHO the way to go. I know that the original "ODN Scanner" was scratch-built from styrene and was one-of-a-kind though, so that's kinda ironic... :rolleyes
After all, i would say that the possibility to do multiple copies
was the reason to do the resin casting for me. That way, there is always the option to cast up a new set of parts in case you screw something...

Additionally, i knew from the start that i might want to do different versions of this prop, so thats another reason.