56105-H5025 is not the strut. It is the shock absorber cartridge.
Bprojects sells them. Owner Endo is a club member here, and is reputable.
http://www.datsun1200.asia/category/select/cid/406/pid/9132KYB 362001 can be purchased out of the UK.
Koni 86-1714 can be purchased out of Louisiana, from
Classic Auto SparesSome VW shock cartridges fit. Get Bilstein (1.507 in) or KYB brand at about 1.5 inch outside diameter. Tokico and KONI are too big in diameter to fit inside the Datsun 45mm strut housings. Jetta shocks fit right in, but have about 32 mm (1.2 inch) less extension travel, but the same travel on bounce. Or course they will ride rougher as do most aftermarket shocks. Cut the strut tube 32 mm and rethread.