Thanks VK5RC and ModemHead.
After several hours of hand filing, I now have the spacers on the top half.
After re-assembling, the spacer on the lower half broke off.
Yes Twoflower, I tried re-enforcing one of the spacers but it did not work.
To save time, I bought some more spacers. They are on the way.
The broken spacer is on the right by the holes for the input jacks, picture taken before it broke
.
While I had it together, it worked -mostly. The 'setup' and 'backlight' keys did not work