You can create a saved search on ebay, wait and hope some eventually show up. They won't be cheap though.
Oh right. It's been so long since I used eBay that I forgot entirely about saved searches.
I'll definitely do that, and keep looking for other sources/options.
There's entire nixie tube forum communities out there.
Oi've no doubt, but where? I'm coming up blank.
Antique electronics forums like radios... I remember a Google group. There was one on reddit 🤮.
For questions about component-level electronic circuits, tools and equipment.
1: Be nice.
2: Be on-topic (eg: Electronic, not electrical).
3: No commercial stuff, buying, selling or valuations.
4: Be safe.