I have been looking all over for one, and most seem to be about $50 bucks. I noticed the 3800 and the ls motors use the same gm oil cap. Found this site, they are only $30. I've dealt with them before, and was really impressed...figured i'd post it up incase anyone was looking for a cheaper alternative (it does have plastic threads, where most of the expensive ones are metal...but our factory is plastic so I don't think its an issue)

ZZ Performance