Looks like there was one for sale a little while ago.
https://machinerysales.cheffins.co.uk/lot-details/index/catalog/448/lot/219962/1971-Land-Rover-Series-2a-Air-Drive-Harrier-Reg-No-WPP-101J-Chassis-No-27706819G-This-is-the-Air-Drive-Harrier-prototype-based-o?url=/auctions/catalog/id/448/Cambridge-Vintage-Sale-Sale-5-Commercial-vehicles-classic-cars-vintage-classic-tractors-at-Machinery-Saleground-Sutton-Ely-Cambs
Looks like we've missed it though.
Here's someone who's made one a bit more recently:
Well when you think that the very first Landies were designed for farmers with power take off to run circular saw etc, I think some of them even pulled ploughs!!