There are quite a few firms which do carded darning wools and similar, a lot of whch is excellent for various bodies. Some blended wools are also excellent for this the original Chadwicks is a blend of wool and nylon;

I have found some of this to be very good indeed;
http://us.knitsmc.com/yarns/regia-2-ply
http://www.amazon.com/Regia-Darning-Thr ... B006MC6MRK
http://www.yarnsupply.com/regia-darning-thread-.html
http://www.amazon.co.uk/Stancraft-2779- ... B004FZVOWE ( may not be available there, search for "Stancraft" darning wool)
Lureflash have sold a range of yarns for quite some time;
http://www.fly-fishing-tackle.co.uk/aca ... RoGAVHBxoA
Some polypopylene yarn is also very useful, often sold as "Superbug" yarn in the UK. I have a very large selection of stuff like this and have found it useful for all sorts of things. I once got a very large sack of stuff like this at a "Flea-market" for very little money, and I have been using it ever since. A few cards of stuff, but I have a great deal more;

Make sure to also search for "Stopfgarn";
http://www.ebay.de/itm/Regia-2-fach-Soc ... 0876074186