Sorry for the delayed response, been out mowing me lawn...LOL
For the Kirby engine I got all the bolts/screws/nuts/washers from
Classic Fasteners - 1/75-77 Grange Rd, Welland SA 5007
https://www.classicfasteners.com.auFull range of all the old UNC/UNF bolts and screws etc.
I ordered them online and picked them up. All neatly zip locked in separate bags. If you are not in the Adelaide area, they do deliver.
Gaskets I got online rzpartssurplus (off ebay I think)
Tecumseh Gasket kit #33233,
piston ring set #27565