I thought T1 was actually the smallest size in the spec (0.81mm across).
This german manufacturer does them and has a UK phone number on their
http://www.wiha.co.uk , the US pages at:
http://www.wihatools.com/278serie.htm are a bit easier to use.
I haven't used them.
RS do some very-tiny Torx drivers as part of a set: their partnum
157-1581, over at rswww.com. That said, the Wiha drivers I've used
are generally *very* nice, but the 4mm-hux-shaft ones I have don't
go down to anything like as small as T1.
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