Ahhh, I see...
The Intruder 800 uses a sort of odd mounting system, with two studs going right through the triple tree to mount the headlight bucket. So any headlight made for them will fit only them. A company in Norway sells kit that has two small headlights side by side, but it is REAL expensive, about $400 with shippping IIRC. If you are interested I can try and find the catalog.
There are other options. One is to remove the headlight bucket, scuff it up, use etching primer, then paint it the same color as the bike. Looks trick. Or you can get a universal aftermarket headlight from Arlen Ness or any number of manufacturers, and make a bracket to make it fit. Or, if you don't want to make one yourself, bring the new headlight to a local machine shop, show him how your current headlight mounts, and he can easily machine an aluminum block to use the verticle holes in the triple tree and the horizonal mounting bolts of an aftermarket headlight. Thunderbike in Germany makes some blocks that allow an aftermarket light to mount to the Intruder, but again, they are expensive as hell with shipping across the ocean, so it is cheaper to have someone local make one.