I have a Givi Monokey top case on my motorcycle. At some point the rubber buffers (spacers) that fit in the mounting plate wore out, and my box would make pretty loud clunking noises when riding. Givi does make replacement buffers (part number Z126), but they don't sell them online and I could only find them on Ebay from international sellers.
I'd heard great things about Sugru, which is a kind of rubber that comes in a sealed packet, and air-cures after you mould it. It has tons of uses, and I figured it would be a good candidate for making my own buffers from scratch. You can get it on Amazon. The Sugru comes in individually sealed packets. I bought the Black/White, 8-Pack, which has 4 each of white and black ones, so I'd have some white Sugru for other purposes. But it comes in a Black 3 pack, which is cheaper:
Sugru did the job perfectly! One pack was enough for the two buffers that were missing. The box is totally secure, and the buffers look factory made. I don't have any photos of the steps, since the whole process took less than 5 minutes. Here's what I did:
Here's the result; the two new buffers I made are circled in red: