I fitted a half set of grab on dense foam sleeves, then cotton taped over the rubber,
to keep it from sun, drying and shredding.
Its possible to glue Leather onto those sleeves then install them.
but Aero cable routing makes that rather difficult.

that was the 80's. Now I double wrap my trekking bars,
I reuse the older tape as the 1st layer..
Drop bars being gripped mostly on the top, a double pack of padded tape , and use i roll cut in half
you can wrap the upper portion 1st, put some of those Gel pillows on top of that,
then wrap the whole bar with the 2nd pack ..