Sight glassoptions uk?

[Bottles]

Hi all,
I'm slowly putting together a Flute column using 4 inch sections joined with triclamps.
Looking to see what options there are for sight glasses in the uk. Also options that don't break the bank? I hope to use 3 inch, as i have read bigger is better?
Are there any sources in the uk for boroscilicate or Pyrex disks. Looking on ebay nothing comes up in the uk. My thoughts was to use a triclamp to hold it to a tri ferrule.
Other options are weld in sight glasses, starting at £36.50 in the uk. I know about distilling uk and SD in Europe. Sd have a minimum order of £145 to uk.
Are there other options I've not thought of other then going smaller to save cost?
Andrew