If you are sure the Uno at 5V is definitely configured as an open-drain driver
(never pulls the signals HIGH), then in theory you can just put the 4k7 pull-up
resistors from SCL to 3.3V and from SDA to 3.3V. The Uno will recognise 3.3V
as HIGH and the Due won't see any voltage higher than 3.3V. In theory.
I haven't poersonally tested this and the consequences of making a mistake
are a burnt-out Due, so I'd be hesitant to try it. There is probably a better way
to wire things that incorporates protection (using schottky diodes and extra
resistors) that gives peace of mind.