IR Dome for AIM 9X sidewinder

I've often used PETG type sheet to replicate convex lenses.  

It's kinda fiddly, but using a punch and die set, I dish the clear plastic sheet and then use the punch to shear off the dished lens.....sometimes takes a little practice, but at the end, you'll have a clear lens over a voice.  I use the same technique for landing lights.

Works a treat.

Hmmm, i've never tried it myself, but i've seen some people use excess clear styrene when they need to make a lens.

If you have the sprue tree from the canopy, perhaps heat up, stretch and then cut where needed.  Obviously some serious sanding might be needed then touch up with Pledge or similar.  Probably best to sand after heating and before cutting to size.

Just a thought.

I have used a small drill bit. hollowed out the end of the missile. Glued a piece clear sprue into the hollowed out area, then shaped it to the proper contour and a little future to shine the seeker head up.

I coat mine with tamiya smoke.

I have heard of ppl using an old CD shaped to size for that irridescent look.