I have tried these lead-free crystal candle/votive holders that seem an appealing proportion for milk drinks. They have a wide brim to practice latte art, heavy base that adds stability while holding and about a 300ml volume that is great for lattes and caps. The below is a US link but they have a Europe site as well.
Joy Votive Holder Set Medium – NUDE USA (nudeglass.com)
They look lovely but at £50 for two… that’s a bit above my pay level.
That’s not a bad idea! I have a contract with a candle factory and they often have ‘imperfect’ glasses they just ditch so I may keep an eye out for some…