If you associate the affordable and ubiquitous 'Bic pen' with disposable, throw away office culture - think again, as Zo-loft design has added a whole new dimension to desktop utility. Their "Din-ink" series of Bic pen style tops allows you to instantly convert
10 quid for something you should be able to get in the quid shop camping section.
saw these, which look like those you mentioned but don’t know where to buy them.