sissy clamps pop up on ebay and you can get stainless nearly correct bolts or orginals
brake cables also
white are easy to find
black not so easy
its worth while buying old white ribbed cheep rubbish to get ferrules
i have a white pair sprayed with Wikes drain pipe paint black..they seem to be fine

i also did the arm rests and bits of dash in my car with it....doesn't come off
you will need to have the frame welded and the welds dressed, this will burn the paint so a sympathetic touch in will be necessary, all paint and corrosion will need to be cleaned off the surfaces to be welded, ideally the surface would be acid treated to kill the rust.
suggest MIG welding is going to be cheapest but also messy, the welds will be rougher and need more work with a hammer file and emery cloth or rotary tool and small flap wheel than a TIG weld which makes a neater weld (tig welding is the kind seen on childrens park things like slides and roundabouts, roll cages in cars etc)
but TIG welding is more specialist and costs more.
but don't let that put you off. its still a lunchtime job any competant engineering shop or auto welder can do, so shouldn't cost that much
either way it will damage the paint for an inch or so either way
paint is best matched by a paint supplier who can analyse an area, make a match and provide a spray can full or a tin and thinners, find one that still does cellulose and enammels. you don't necessarily want a modern 2 pack or water base paint, althogh i'm no expert in modern paints
ideally you'd purchase some primer from them as well and test both on the underside of the bottom bracket to see if they react with current paint
the top coat paint needs to be feathered in by providing a raised edge to the masking
build many thin coats
wet-n-dry sand then polish.
sand right through in places if you want to maintain a semblance of patina.
think the decals are very dry brittle stickers, mine have chipped off in places
Dave