So that pin is a pretty non standard piece of hardware. It is a same size thread shoulder bolt. The total length of the bolt below the head is ~3.25" and the length of the actual hinge is ~2.75". It's a 3/8" Dia Bolt.
If you can source out a partially threaded bolt so you are not mashing thread into your hinge metal, that would do until you can get one from aluminess. Aluminess is super cool about replacement hardware.
You need something 3.25"-3.5" long with partial threading that would still allow you to get the nut tightened down. Partially threaded bolts have varying lengths of threading. So you gotta find one that simply works. Stainless is what you need, but a steel bolt would get you through until you find a suitable one.
Hope this helps.
Tim - 2013 EB V10 Agile 4x4 SMB PH Ginger Army All Terrain Mobile HQ