For the head light, I think you can use pretty much any standard round headlight. I actually have a buell blast sealed beam mount on my B4. It doesn't cost a whole lot to pick one up from the Harley dealer either. As for sprockets and chains, I usually order them from kneedraggers, but since you're out of state, you can also hit up sprocketspecialists.com for your needs- they have decent pricing for chains and sprockets.
Any REAR 525 sprocket that is applicable to the SV650 is applicable to the B400, but I think you will have to stick with the Bandit 400 specific front sprocket though.