You may be lucky if you contact these people and see what they have got :
Hawco Limited t/a Abbeychart,
Units 5 & 6 Woodside Road
South Marston Park,
Swindon
Wiltshire
SN3 4WA
Contact Us - Sales: +44 (0)1367 711 900 Technical: +44 (0) 1367 711 903 Email:
sales@abbeychart.co.uk
They sell an 11mm diameter sight glass for expresso coffee machines. You would need to check the specification with their technical team. Please post how this goes. If these glasses are up to spec. they may be a cheaper source of gauge glasses than our usual suppliers.