I would assume they'd have been specifically made to use there. If you wanted a replacement the right size and style, you'd probably have to get one specially made.
If you needed to take a model of what you'd want with you, it could be difficult. Genuine portrait coins of Claudius are normally pretty expensive. You might have to make do with an imitation, or a printout of a coin from an online database, like
this one.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis