Early in my time on the CB, I bought a variety of luggage systems, including the Givi 266FZ side arms for mounting a tail bag. I used this system on a couple tours, then switched to a tail-bag mount at the rear seat position. Now I want to get the rack arms out of my basement.
You'll have to buy the Givi 1101 Kit, which puts a little cross-brace under the tail, to which the side arms gets bolted. The 1101 Kit includes everything necessary EXCEPT two - hex-head 8mm x 25mm bolts and the matching nylock M8 nuts ( flange head best, but any will do). The kit seems widely available, and costs between about Euro 30 and CDN$ 75. In the fitting instructions, it's the two bolts #5 and nuts #9 that are missing in the 1101 Kit. Super-easy to find.
I've checked Canada Post, and it'll be CDN$40-$50 for anywhere in the USA. Looks like roughly CDN$100 for the UK. The box is 34" x 8" x 6", and weighs about 7 pounds, if you want to check courier rates from your end. I'm in Vancouver BC Canada, postal code V5Z 1Z9.