Either a tire, a wheel, or a set of wheels would be fine. Ideally it'd just be a single tire, as this would be, by far, the most cost effective solution. My LHS, despite stocking various truggies (including my Inferno), don't stock a single truggy tire. Not exactly ideal.
Also, I've just got in from work, and so have been able to measure the hubs. There is a 14mm hex, with a (plastic) 19mm hex fitment connected to it, though it is easily removed. Does this mean I can use either a 14mm or 19mm, or should this type of fitting always be used with the 19mm 'adaptor'?
Bit annoyed to find that neither were 17mm