Here is some info to help.
The transmission and transfer case used on the international is the same case used on the White halftracks with some different gears on the inside. That means all the bearings, seals and gaskets are the same. For all bearings and seals contact Kevin Lockwood. For gaskets contact me.
With that said I believe the e-brake assembly is the same as the White halftrack. If that is the case then I have a complete assembly for sale with the disc.
The clutch disc and bearing should be an off the shelf Item at a big rig truck parts house. It's a Spicer clutch. Check with them. If they can't help then they should be able to point you in the right direction.
For the wheel cylinders, Get the Wagner part numbers of them and have them cross referenced. Kevin might be able to help you.
BAIV has all the armor, doors etc. reproduced.
Because International halftracks are not common in the state your best chance for parts are in Europe. Here are some links to some part suppliers.
The below are probably the largest European dealers for parts:
http://www.baiv.nlhttp://www.staman.nlhttps://www.lwdparts.comHope this helps.
Steve A.