Will they really not accept a $10 bill or even a $10 signed travellers cheque in the mail?
Money orders are long dead in the UK - what your bank will give you (for that hefty fee) is effectively a certified cheque. Thomas Cook do something similar, but the last time I enquired it was a flat fee of £10.
The only thing I can think of is if you have a colleague going to the US on holiday (or business) is to get him to buy a US money order there from a Post Office and reimburse him. Or possibly a contact in a US university, if you have one. Send him some cash, get him to buy one.
The Post Office here long ago gave up on money orders - they now offer a fairly expensive moneygram service internationally and postal orders domesticly. The latter are cashable overseas but only in smaller commonwealth countries. Banks will provide you with foreign currency cheques, for a large fee, or do an electronic transfer, ditto. Small sums, especially to larger inflexible organisations, are a nightmare, as you've found.
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