Pyrogravures

The better woodburning pens used by wildlife wood carvers etc. have temperature controls and a gazillion tip options as well. One can set the temperature more than low enough to safely texture styrene.

The downside is that they generally start around $100.00 for a complete pen/temp control/ basic tip selection, and quickly go up from there.

Thanks for the suggestions. I've tried the needle in the soldering iron but the biggest problem is the lack of control as the device can't be gripped anywhere near the tip. I haven't yet found a low wattage iron with a short business end that can be used more easily (and I've looked). I've seen some fine tipped wood burning tools, but I shudder to think what a device that will char wood will do to plastic!

Back to the needle and the spirit burner!

Long ago and far away,  I was given a spiffy low-wattage soldering iron.

It was middling useless for most of its alleged functions (jack of all trades and master of none). 

But, it did have one endearing quality.  It had a screw-on xacto-style cruciform clamping head.  This was underwhelming when used with a #11 blade.  But, a stout bit of steel needle on the other hand--that was rather the cat's meow. 

Rug needles seemed to be the very thing.  Sturdy. inexpensive; you could hone the tip on a stone after wearing a burr on the tip--pretty good deal all around. 

Wonder where that iron wound up . . . <sigh>