A few other players were older at their last game when they changed clubs. Not sure of the circumstances of some, whether traded or simply let go.
John Rantall 35y266d Sy -> Fi 1979-80 (330 games - makes Mitchell the third most-experienced player to change clubs)
Doug Hawkins 34y122d WB -> Fi 1994-94 as mentioned
Alex Jesaulenko 34y58d Ca -> St 1979-80 as mentioned
Mick Martyn 34y8d NM -> Ca 2002-03 as mentioned
Johnny Lewis 33y359d NM -> Me 1935-36
Sam Mitchell 33y340d Ha -> WC 2016-17
The following players returned at a new club after a break of one or more seasons:
Syd Barker Snr 36y292d Es -> NM 1924/1927
George Haines 33y360d Me -> St 1925/1927
Len Thompson changed clubs again after 288 games.
Dean Brogan and Ben Hudson were also traded at 32yo.
Thanks Ron.
My first list I was going for 'one-club men' who left, hence why I omitted Rantall, Cloke, Osborne etc who moved multiple times.
I don't think any of those older players were traded as per the modern trade period with the draft.