rusted

I would like to ask for advice regarding diagnosing rust damage and options for treating / repairing an otherwise nice and light Univega Alpina 504 frame. One chain stay, the chain stay bridge and to some extent the bottom of the main triangle are affected (see attached photos). Presumably...

Where are peoples “go to” place for getting replacements bolts, fasteners….ally, steel, Ti……or is eBay your friend…?! UK 🇬🇧 based.