The blue traditional tableware is Bing & Grondahl's Blue Fluted dinnerware and closely corresponds to Royal Copenhagen's service and therefore the two fit nicely together on the table. You can find Blue Fluted by Royal Copenhagen here.
Bing & Grondahl produced their blue traditional service from 1886. It has the name "Blue Traditional", because Royal Copenhagen had the rights to the name "Blue Fluted", but both are based on the German muschel style, which was developed in Meissen, Germany, in the 1740's. Muschel means clam and the style is originally inspired by Chinese porcelain.
B&G originally produced the blue traditional dinnerware fluted like the blue fluted from Royal Copenhagen, but later they also produced it on the popular dinnerware with seahorse and dolphins used for the Seagull dinnerware.
Because the blue traditional dinnerware from B&G and the blue fluted from Royal Copenhagen are very similar and can easily be used together to supplement each other, if you have not been able to find extra pieces for one set.