If I want to buy gas shock absorber for volvo 360, where can I find it

Your best bet is the Gaz adjustables that Classic Swede sells, none of the original aftermarket suppliers sell gas ones anymore, only oil filled, sadly.

Where shocks can be bought? expect classic swede
have not found any shocks avail from norm shops

I've got them from ebay in the past.

Born-Built-Beauties also sells GAZ stocks.
Sometimes one can find nos shocks on eBay or secondhand sites.