YSS Shock Absorber rear MONO J diameter?

Schaltroller / Classic Motoscooters Vespa Smallframe
1

I would need a rear shock with <45mm diameter width (top part tube) in order to fit with my setup. Any one with possibility to measure the upper part diameter on the shock?

An example picture here: http://www.sip-scootershop.com/community/members/Simppa/files/monoshock1.jpg.aspx

 

2

Sorry for thread hijack! I would also like to know what performance rear shock absorber has the smallest diameter. When I mount a Schwalbe 120/90-10 it slightly rubs my Bitubo. 

3

Diameter inspected. It's 52mm which is too big for my setup.