Hi Dave, I think it was one of these, can’t remember which now!
I do not recall having to alter the nut.
From Simply Bearings:
2 x 0.75×1.12×0.18 inch Nitrile Rubber Rotary Shaft Oil Seal with Garter Spring R21 / SC (0.75×1.12×0.18_SC) = £3.98
2 x 0.75x1x0.12 inch Nitrile Rubber Oil Seal Type R21 / SC (0.75x1x0.12_R21) = £3.78