I have seen transparant plug wires, but I thought they were a no no. The ones I saw had wires ending at random locations so that the spark would jump from then end of the wire back to the main passthrough wire cluster. And people quit using them for a number of reasons like
1. All that spark jumping lead to decreased spark at the plug
2. Poor insulation against them shorting out through the sides
I actually saw a pair on a non-running '53 dodge PU once and they were all cracked, and looked like cheap plastic.
Never seen or heard of transparent dizzy caps, but I would have to assume that somebody made them, and people quit using them for similar reasons.
ron