You can make them yourself, by starting with washers and trimming them down to size, To do this, you need one set of spacer blocks as a template; you need two sets of blocks total (six pieces) and the string gets clamped between them. Fortunately you have one set already- I see it on your locking nut now. (it's pretty common to have one set of spacers stuck on the nut- pry them off and you're ready to go).
The bolts are likewise standard metric hex-head bolts (4mm? I forget)
Here's a pic showing the trimming process: