At this point unless you go custom or happen to find used addons there isn't much anymore.
ARB for bumpers unless 4speed makes some more.
Gobi, ARB, Frontrunner, and either Rhinorack or EZ-Awn for roof racks/baskets/platforms.
Safari snorkel or Ebay chinese special snorkel (they are the same really, I had the Ebay one and found nothing wrong with it so for $160 shipped it's far cheaper than the $400+ Safari branded one)
Nothing really specific to the H3 for lighting mounts/brackets unless you go old stock with the A-pillar brackets for the 50 inch light bars. I have a couple pairs but right now I'm not planning on letting them go, others might be willing.
Look through the supporting vendor section on here for UCP, though with a welder it's easy to make a custom jobbie.
The build threads are going to be your best bet for seeing what others are using and to get ideas. Really you should start out by determining just what you want to do with your H3 and where you are actually going to take it. Don't just start bolting on goodies. If you're mainly going to be on reasonable forest roads then you're already good to go. You don't need UCP even until you know you're going to be going places that the risk of scraping your belly is real. Rock crawling needs UCP and sliders, but that is pretty much it to start out with. If you'll be going places that you are likely to get stuck, start out with a set or two of maxtrax and a shovel. Winches are great and all but are expensive and heavy, never mind the weight of a winch bumper if going that route. I have one only because I got the bumper for a steal and the winch was $200 at the Harbor freight parking lot sale as an open box item. All I've used it for really was to pull a tree down last summer.
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