Here's the deal as I see it Les... The security of the HISS system is in the ECU and the key (which, as well as a cut blade, has an electronic transponder built into it). The two units communicate wirelessly to some extent, via an antenna, which is the plastic raised ring around the ignition keyhole marked 'HISS'. The antenna isn't machine specific or coded as far as I can see and therefore it's transferable without any aggravation. But that leaves the key/ECU interface, which is very coded and very specific to each other.
The Honda HISS key blank costs about £60. There'll probably be around 500 or 1000 different key numbers, in other words different serration sequences cut down the blade so they mechanically fit and turn, so a fairly limited number, but you'd get bored fast waiting for the right key to accidentally turn up on eBay! In any case the interface with the ECU could easily be a million to one shot, which is why the HISS system is CAT 2 rated and why they cost a fortune to replace even second hand.
In order to programme or re-programme a key to work with the ECU, you need to bugger about with a mini wiring loom, connect the ECU to the battery and then put your original key in the ignition to turn on the re-programming function. With the function started and a light flashing on your dash, you remove the master key and insert each new key into the ignition, turn it on then off and then it learns the code that the ECU is sending to it and that's that... programmed. Usually, that wouldn't be a problem, because somebody would have lost a key, needed a new one and so rung Honda. Honda would have cut the new, unprogrammed key to fit the lock using the key number (which of course we all have written down and in our owner's papers) and then sent it to the dealer for programming on the bike, pretty much as above.
The problem, is that the two keys you want to reprogramme won't turn in the same lock as the key they have to learn from. So we can't fit the new barrel to your bike and sort it, because the old key won't turn in the new lock barrel to turn on the ECU into programming function, so we have to get creative with what we've got. So...
Re-wire the existing ignion (on or off the bike). Start the programming function with the original key then remove and take it away. Next the two new keys need three things to be programmed... 1) proximity to the antenna, 2) an earth (the key blade must be earthed during set up. By nature, it would usually be earthed through the lock barrel but not today eh!), 3) the ignition has to be turned on and off with the key. Piece o' piss eh? Well, yes, provided Simmo's keys (by magnificent happenchance) go into the lock and turn it and... well... there's a bit of creative thinking required if they won't. IF they don't, as far as I can figure, t'll have to go something like this...
We'll start the re-programming function using the good key on the original, damaged barrel. Remove that key at the right time as is required. Insert a screwdriver (or other piece of similar metal) into ignition barrel to imitate the new key. There will be a wire soldered/attached to the screwdriver at one end and a wee croc clip on the other end, to clip onto the key (and thereby earth it to the inside of the barrel as Soichiro San intended. The set up routine is basically, connect the new key as above. Place it next to or on, the antenna. Turn the screwdriver in the lock to the on position and then off as required. In essence, the key, antenna, ECU interface is maintained by proximity and the ignition sequence is done by the scredriver, but that shouldn't matter becuase the ECU can't tell the diiference between an earthed metal key turning in the lock and an earthed metal screwdriver. As a matter of fact, the ECU shouldn't even care. What it's looking for is communication twixt key transponder and ECU at the same time as the ignition being turned on and off and it has that.
You should be able to set up 4 keys like that (max)
So... why have I just bored everyone to death with my theories... because if anyone wants to help you with it whilst I'm unable to get there, they now know what I'm thinking and at least it's not that difficult