HP-67 tantalum capacitor: where to buy it?

[Zaphod]

Check the auction site out for 182307853956 if you're in the UK
(No connection)

Select 6.8uF and 16V

5 for 99 pence

It doesn't have to be a tantalum, you could use a standard electrolytic cap of the same value.

As said, the rated voltage is immaterial broadly speaking (as long as the rating is higher or equal to the original it's fine)

But beware and ensure you get the cap the right way round , both types will explode if reverse biased (connected the wrong way round)