As far as I remember Band-X (http://www.band-x.com) do this.
Dave.
The last time I looked at Band-X (about six months ago) their pricing was ridiculous... I believe they wanted >$100/Mb, on a 100Mb commit, for Aleron or HE bandwidth. It should be noted that Band-X blocks potential buyers from learning the actual name of a transit provider, up until the very last moment (signing contract). They hide their transit sources behind anonymous "Company A, Company D" and so forth. Getting the actual name of a source from the band-x sales rep was like pulling teeth.
-Eric Kuhnke
eric@fnordsystems.com