Hey Switched,
Have you used this place?: McMaster-Carr
Or here (even though its ebay, don't know if this will help?): 3/4" OD x 5/8" ID CLEAR ACRYLIC TUBING 6 FT LONG TUBES - eBay (item 190477788690 end time Apr-09-11 10:23:48 PDT)
Don't know if these places have what you use or need to use and...