That's not a dedicated Discovery 1 rubber hanger for sure so you'll have to find some similar generic one if the original type are not good which means that maybe the exhaust was replaced too
As you have found out these fittings come in different lengths, thats possibly because there’s 3 change points with these exhaust fittings for the Tdi.
You should have 3 of these items fitted, if so take one off as a pattern or take some measurements when u go shopping
My petrol 97 disco still has the original rubber but now holding a stainless system and without any issues from these genuine parts.
The genuine part number on my 1997 vehicle is NTC5582, which is also applicable to the Tdi, so u could try this … but then because of the change points the number could be NTC3650 or ESR3172
There are or was some universal fittings available with two extra holes to fit as either vertical or horizontal, do they hold the weight of a disco exhaust who knows.