I sent some emails to Amsoil, Uni Filter and Twin Air with the following results.
Amsoil don't seem to do filters for Transalps and they have a very poor idea of which of their filters fit which bikes.
Uni filter do not produce a filter for the Transalp
Twin Air do a filter for the Transalp. They put me in contact with a UK distributer (JAM Sports 01252 725335) with which I have placed an order - they said it will around £10 which includes oil and filterbox cover apparently.
If I had had no success from Twin Air I would have tried the above two suggestions. bandcexpress.co.uk do a filter for the Transalp from Moto Air. Pipercross do not list the Transalp as one of the bikes they do filters for, but that does not mean none of them would fit.
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