I have a plan. That's a dangerous thing.
Around our house we have vast numbers of milk-bottle tops. For some reason we don't put them in the recycling bin. In fact it seems that very few places recycle them, so maybe I have to step up to the mark.
These things are HDPE -- high density polyethylene -- AKA recycling number 2.
Now from reading the Wikipedia page, and a few others, I find that the melting point is somewhere between 130C and 180C, and I can find no reference to any hazardous gases that may be given off.
That's too hot for a double saucepan, or is it... Water boils at 100C of course, but oil doesn't. In fact 180C is the bottom end of a deep-fat fryer's range.
So I plan to make a positive mould out of modelling plastic, or maybe balsa. Then use either sand or salt as a negative mould, as I learned a long time ago in metalwork classes. I'll melt the bottle-tops in a tin can in the chip-pan, with a thermometer to make sure it stays around 150C-ish. When it's all melted, with great care, I'll pour the plastic into the mould, wait for it to set, and then remove the finished case. If I used salt for the mould, any bits stuck to the case will dissolve off in warm water.
Now the reason I'm posting this now, rather than when I can gleefully post pictures of my finished (green) case, is that someone here may know something I don't. So if this plan is horribly dangerous above and beyond playing with super-heated fluids, please tell me.
At least by typing this up the paramedics will have a record of what exactly it is fused to your skin, which may also prove useful to the coroner.