Thanks to this post:
http://forums.equipped.org/ubbthreads.php?ubb=showflat&Number=109385

I found this (go to 'handy tubes'):
http://www.sciplus.com/category.cfm/subsection/7

Exactly what i'm after. I can never use up 20, but is anyone interested in a few? Maybe a group buy?

All kinds of good stuff on that site!!!!!
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"One should not increase, beyond what is necessary, the number of entities required to explain anything"
William of Ockham (1285-1349)