Hi Sanjiv. Farm supply stores have been best for me when trying to find parts for the heavy lift belts. I got hay baler conveyor belt from Tractor Supply. It can be cut with a utility knife. Rivets are often used, but I used short carriage bolts for my hip lift belt. I have found that farm supply store staff are often interested and very helpful when they find out what we are going to do with this stuff. They have had specific hardware suggestions that have been helpful not only for chain lifts but for other lifting applications such as optimizing adjustable kettle bell handles.
A steel fabrication shop should be able to help you with the bar. For a solid bar cold rolled 1045 steel was recommended because it is stiffer than 1038, but I don’t know what others in USAWA use for their bars. Diameter needs to be 1-15/16″. I think you will outgrow a pipe/hollow bar pretty quickly.
And hopefully you can find a local gym that will let you bring in your bar and lifting rig so you can load it up without having to invest in a bunch of hundred pound plates. You might even find others that are interesting in giving it a go.
Good luck with your project!