FCP has always been good to me. Ive been ordering from them since about 2008. Used them for all the Volvo's ive had and now use them for the VW too. That being said, they arent the only parts supplier for our cars. I had a quick look on Rockauto and they list the 16v valve cover kits. If you struggle with FCP on this order you can always get it from Rockauto and try FCP another time.
https://www.rockauto.com/en/catalog/volvo,1990,740,2.3l+l4+dohc,1419500,engine,valve+cover+gasket,10710