So based on the time frame you've given, you're interested in life in the court of crazy King Charles?If you are looking for costume information more specific than what is offered by the general overview costume books, identify the personages that are important and go looking for sources that will describe accounts of their households.
Poking around a bit I came up with: http://orb.rhodes.edu/encyclop/late/France/LMFrance.html - Late Medieval France A Guide to Online Resources; Dana L. Sample
and a book in her bibliography - Famiglietti, Richard C. Royal Intrigue: Crisis at the Court of Charles VI 1392-1420. New York: AMS, 1986.
There are also a number of surviving works of art from this period on the Web Gallery of Art. Some artists that come to mind are:
DALLE MASEGNE, Jacobello (? -1409) Italian sculptor (Emilia) http://www.kfki.hu/~arthp/html/d/dalle_ma/index.html http://www.kfki.hu/~arthp/art/d/dalle_ma/legnano.jpg
GADDI, Agnolo (1350-1390) Italian painter (Florence)
PARLER, Peter (1330-1399) German sculptor (Prague)
Also on Parler, it's german but it's a really cool exhibition catalogue. There are pictures of the back of statues and lots of details.
Die Parler und der schone Stil 1350-1400 : Europaische Kunst unter den Luxemburgern : ein Handbuch zur Ausstellung des Schnutgen-Museums in der Kunsthalle Koln / hrsg. von Anton Legner. Koln : Museen der Stadt Koln, 1978.
SLUTER, Claus (c. 1350-1406) Flemish sculptor (Burgundy)
SPINELLO ARETINO (1345-1410) Italian painter (Siena)
Building the Ark, book of hours (1422) - http://www.kfki.hu/~arthp/art/zgothic/miniatur/1401-450/01f_1401.jpg
Charles VI Talking to Pierre Salmon (1412) - http://www.kfki.hu/~arthp/art/zgothic/miniatur/1401-450/01f_1403.jpg
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There is certainly a fair amount of change in costume over this time period. In 1390 you still see the padded chest / wasp waist silohuete that is described as becoming popular in the 1360's. By 1412 houpelands a la Tres Riches Heures seem to be the vogue. I would start by identifying what shape you want to be and then going to the costume books to help work out how to achive that shape.
Mitake.