My new springs from Eaton came with them. I have also run the TEFLON type full length liners with no problem.
https://www.speedwaymotors.com/shop/street-leaf-spring-pads-buttons~65544-1-31215

Drilling in to leaf springs is not an easy job, the spring shops punch press the holes. It makes for a smoother ride and much quieter. I say it well worth the trouble to have them or the liner installed. Never had a issue with the liner strips or u-bolts coming loose. I went with new springs so I could get custom spring rates for a smoother ride.