If you get sereis 3, or early defender hinges you don't even need the brackets as the top hinges are drilled to accept a mirror arm and you just bolt it directly to the hinge.They look all wrong. Once you get the right hinges there is a bracket that fixes the mirror to the hinge bolts, the LH side is easy to get and the other is impossible. You may have to cut up a LHS and re-weld it to make a RH.
https://www.johnrichardssurplus.co.uk/door-mirror-arm-mounting-bracket-l-h-347705.html
True, but beware of the head of the screws.Excellent, might try drilling two wee holes in the existing hinges .....nothing to lose.
Weld a couple of tractor stalks on em.Thats the kind of thing I was thinking of. The doors close quite well, so am not that keen on new hinges, although the mirror situation is driving me mad, I use a lot of single track roads with a trailer, so good wingys are a must !