"“Hello. Have you ever considered sourcing spare parts for these [pump vacuum flasks]? Mine has pinholes in the bellows which makes it harder to use but is fine otherwise. The bellows are very easy to change. You might find there is a market.”
"“Dear Customer,
Thank you for your message, We don’t sell parts separately.
Regards
Customer Services”
What a frustrating exchange!
Care to share which brand this was Matthew? 
I would, happily - if it weren’t brandless and I was just messaging some random eBay seller which has sold a lot of them. They just need to talk to their supplier and they’d have a new revenue stream.
(The one I can name is Ecoair, who took a dehumidifier spare part off their website because I had the cheek to order it. They tried to cancel my order but I kicked up a fuss.)