What, he's stolen (or borrowed!) Jan's tights ?!!!
Geo, the 'invisible' mending thread mentioned by Vic is available in a number of colours, including a 'smoke' shade, rather like a dark steel colour, and I think a metallic grey colour. It's not a 'woven' thread, like cotton, but similar to mono-filament 'Nylon', so no 'hairs', and a 'bobbin' or reel will be enough to rig every model you'd ever like to build, and then some, and can also be used for antenna wire etc too.
It also saves 'getting it in the neck' when Mrs. Geo discovers you've ruined her best tights by pinching a thread from them !!!