Here you go, again you must apply on the inside. Do a couple of lite layers at a time and you can control the translucency that way.

Tamiya 86045 PS-45 Translucent Purple Spray Paint, 100ml Spray Can https://www.amazon.com/dp/B0006SG28U/ref=cm_sw_r_cp_api_i_FQZNT8Q6601FJ8X3M1BQ

Ps. I have used a different color for my shell, so not sure how close to atomic purple this is, but you have control of the translucency