source for 6-8 kD cutoff visking dialysis tubing?

[Song]

Hi, netters!
Our local Swiss distributor (Bender and Hobein) for visking dialysis
tubing has decided to close shop, leaving us without a source for Union
Carbide visking dialysis tubing with 6-8 kD molecular weight cutoff.  We
used to be able to purchase rolls of 50 ft with various different widths
(12-65 mm flat width) for 50 to 80 SFr (about US$33 to 53).  We use a lot
of this stuff, so we would appreciate a reasonably priced distributor
(read:  not Spectrum).  Can anyone suggest alternative sources for such
dialysis tubing, either in Europe or in the U.S.?  We can still get the
"normal" 12-14 kD cutoff tubing at reasonable prices here; it's the 6-8 kD
cutoff tubing we're having trouble finding.
Many TIA!

Song Tan
Inst fur Molekularbiologie und Biophysik
ETH-Honggerberg
8093 Zurich, Switzerland
email:  tan at aeolus.vmsmail.ethz.ch