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Here's the deluxe option. The payback terms might be a bit long though, £9 plus postage is a lot of ends of toothpastes. https://www.aktlondon.com/collections/all-products-atom/products/the-assistant
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Artists call them tube squeezers or paint saver keys. You could get one online from an arts supplier, I’m sure they could use the business.
E.g., no affiliation https://www.pegasusart.co.uk/tube-squeezer-paint-saver-keys-3-sizes-large.ir
My wife, for some reason only known to her, throws out my tube of toothpaste when there's at least a week's worth of usage left. Not much goes on an electric brush head.
My mother used to use those blue keys on our toothpaste tubes when I was a kid but Primula don't seem to do them anymore and they've been cancelled.