If you're looking for really top of the range then try - http://www.dpamicrophones.com/eng_pub/index.html

Alternatively take a look at -

http://www.judicael.co.uk/articles/violin_pickups.pdf

I've been using AKG micromics including the C411 http://www.akg.com/products/powerslave,mynodeid,164,id,272,pid,272,_language,EN.html attached to the violin body and the C418 http://www.akg.com/products/powerslave,mynodeid,15,id,275,pid,275,_language,EN.html clipped onto the chinrest. These can be used with a battery pack, phantom power or a radio transmitter.

Mitch