Need new TOPO parts, first are the push rivets and ribbed shank ones. Go to www.mcmaster.com Search rivet nylon. Buttons are at digikey.com

This is the push rivet

This is the shank rivet. Be sure to look for other hardware here as this was their source for many pieces of hardware.

Old part number is 450-1057-nd new number for green  is 1825068-5

Old part number is 450-1054-nd new part number is 1825068-2