Sidi's (and others) come with replaceable heel pads. I use "
claw nuts" to Sidi-fy my Shimano shoes so that the heel pads can be replaced, and use table leg pads with normal plus drive bolts to attach them. At first I just used pieces of rubber but the table leg pads are better.
https://www.bikeforums.net/20060688-post66.html
I use the same table leg pads on my Sidis too because they are cheaper and no worse
https://www.bikeforums.net/road-cycl...l#post22302202
Here are the pads on aliexpress (no affiliation)
https://www.aliexpress.com/item/4001364276979.html
If I have worn through the carbon sole a bit before replacing the pad, or at the toe of the shoe, I use a bit of carbon fibre usually with epoxy (rather than proper carbon fibre epoxy which tends to be toxic and is more difficult to source) to patch it first. In the past I have used proper carbon fibre epoxy from Carbonology in the UK but I don't think they sell the kits anymore.
https://www.bikeforums.net/road-cycl...l#post19470005
Buckles sold as roller skate buckles can be used to replace cycling shoe buckles.
https://www.bikeforums.net/22043213-post103.html
https://www.aliexpress.com/item/1005003311108436.html
If the cleat nut goes (becomes bonded to a cleat bolt) then they can also be replaced with a claw nut.
https://www.bikeforums.net/22309060-post131.html
If the sole parts from the uppers, I use a file to rough up both sides (perhaps scraping old glue out first) and then AB epoxy, and G clamps or sprung clamps or both to glue them back together.
When the heel interior becomes frayed I sew them up again.
My shoes generally look awful (other than the Sidi's which wear very well) but last pretty much forever.
There are also some very indestructible SPD-SL cleats (that are dangerous when new because they are slippery) available from China now.When they are a bit roughed up, I don't find them to be too dangerous and they last twice or three times as long at about 1/5 the price of Shimano's cleats. Nice colours too
https://www.aliexpress.com/item/4000409970751.html?
And, looking through my repairs, I had forgotten I use heel pads to replace helmet liner pads. They are good and cheap so I just ordered some more.
https://www.aliexpress.com/item/1005002857176293.html