Doing a little homework to find actual HAL dimensions, I was surprised to see the button and bezel are within just a couple millimeters of the genuine prop — a Nikkor f/8 fisheye lens. We just need to dress it up a little, repainting the bezel from black to silver…
Squeeze these two tabs inward to release the button. It’s possible but a bit tricky to do with finger pressure alone, so you may want to use needle-nose pliers (gently!).
There may be a slight oily residue on the bezel (mold release from manufacturing, I suspect). This can be cleaned with dish soap and water, but be certain it’s absolutely dry before painting!
The key to a good paint job is to use several light coats rather than one thick gloppy one. Allow 10-20 minutes between each coat to allow the paint to set up a bit. Make sure the paint is well-mixed prior to starting, and periodically give a few extra shakes while working.
Hold the can about a foot away from the subject, and spray a light mist in three or four overlapping horizontal passes, starting just off one edge, working straight across and past the other edge. Yes, you’ll end up with more paint on your dropcloth than on the item, but it’s key to getting a flawless finish. Go fold laundry or something, then come back for another coat (perhaps turning the piece for a different angle). Repeat until there’s a few solid coats with no black showing through.
Allow the paint to dry for at least a couple hours (ideally overnight) before handling the piece. You can work ahead on other steps in the interim.
Model paint and a steady hand is an inexpensive approach. My craft stash happened to include some black vinyl contact paper (shelf liner) from a prior project. I used the clean, factory-cut straight edge toward the front of the lens, and trimmed at the back with a hobby knife.
This doesn’t include the extra materials for the optional black ring (sandpaper or masking tape, black model paint or contact paper) as I already had suitable items on-hand. Your tally may vary, depending on what steps you take and how you adapt this to your own supplies.