Well, as no one else has offered any words of wisdom I’ll stick my oar in for what it’s worth but my machine is only 50 years old and I have no direct knowledge of Scott drippers so I might be writing complete nonsense!
I am assuming from the mention of washers that we are talking about glass tube rather than a flat window.
The trouble is that many firms just do not want to be bothered with penny number quantities so my first line would be to ask at your local secondary school or better yet, if you have one nearby, University. The chemistry department might well have some suitable glass tube, ask the head of department if you can see a lab technician, it is they after all that look after the everything. Even if they have nothing suitable they should be able to point you towards their suppliers and educational suppliers are more geared to providing small orders.
If that fails then there are lab suppliers on the internet but again quantity might be an issue. The model engineering fraternity use glass tube for water gauges so buy a copy of “Model Engineer” and trawl the ads.
If all else fails post the dimensions of the tube you need I’ll prod a few of my contacts.
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