I was looking for these a few years ago and went with Konis when they were NLA - it seems my eBay search is still active 
Ps. Beware of Google when searching for shock absorber brands
Datsun 240Z Early 260Z Tokico Illumina Front& Rear Adjustable Shock Absorber Set | eBay
To change the damping force, simply insert the Illumina adjuster (part #TO 00102) into the top of the rod, and turn it to any of the five numbered settings. Datsun 240Z/Early 260Z Tokico Illumina Front & Rear Adjustable Shock Absorber Set - 2X BZ3015 + 2X BZ3016.
www.ebay.co.uk
Ps. Beware of Google when searching for shock absorber brands