any wire rope maker can make you some if you contact them and give them measurements, NOT sure how cheap this will be
have you thought about maybe switching to chains , rather than wire cables?
won't be as light, but can be just as strong or stronger and chain can be had at most bigger chain like hardware stores(so can wire rope, but you need a special crimp-er to do the eye ends the RIGHT WAY)
many yrs back, thats what OEM's even used, I still have a few stands with them even chains rather than straps that attach to the tree, although I think straps make for better fitting to the tree's than the chains did, but for just platform holding up like, chains should work just fine, if your OK with the added weight?