generally it is not recommended to shim your oarlock up. The strength of the shaft is not made to withstand those increased forces at the top. Or so I am told.....
You have two options. One is AAA and one is DRE. They have very different geometry and are not interchangeable. AAA is if your frame is wide (or the tilted tower position) and you want to bring the lock in. Use DRE for the opposite. We started with AAA and had to switch to DRE for better geometry.
both of those can be ordered to any height.
Down River Oar Tower | Oars | Accessories
Note for both you also need the tower base, and it is frame brand specific.
Edit- dang it, I just read the comments and saw your photos, so this advice won't work. I will leave it for future reference for others. I would probably switch locks to the aluminum NRS ones, as they are stronger, and shim the heck out of them! Get a shit-ton of washers from NRS (from the spring set) to use as shims if you can find nothing else.