The Times of London edition for July 30, 1807 contains the following information attributed to newspapers received from Hamburg:
"Antwerp, July 1 -- The Westphalian Regiment arrived here a few days ago. Almost all the men are from the North of Germany, and do not understand French. About two days after, the Irish Brigade, about 1,200 strong, entered Antwerp. It consists of grenadiers, voltigeurs, sappeurs [sic], etc. and an excellent band of music. This fine corps wear short green jackets, and caskets [sic], with plumes of feathers. Their eagle is decorated with a golden harp, and this inscription "The Emperor of the French to the Irish Legion."
It would be interesting to see the original report in the Hamburg newspaper, or perhaps even a similar report in an Antwerp journal.
I found some images, maybe of interest
Not sure if this is still of interest: There seem to be two articles in the "Allgemeine Zeitung" related to this:
The first is a brief note in the issue of 6 July 1807:
"In Antwerp, two more ships of the line, the Caesar and Duguesclin, were launched on 20 and 21 June. The Regiment Westphalen of 1100 men, commanded by the Hereditary Prince of Hohenzollern-Sigmaringen, had arrived in this very city, and the first Prussian regiment of 1630 and the first Irish regiment of 1100 men (also consisting partly of Prussians) were expected."
The second article is a lot longer and appears in the issue of 11. July, dated "Brussels, 27 June":
"I have just come from Antwerp, where I stayed for a fortnight. There is now a liveliness there that has not been seen for many years, and an activity that will have incalculable advantages for the whole of Belgium in terms of trade and commerce, if only we enjoy peace again. The city is teeming with troops. A few days ago the Westphalian regiment arrived; it consists of two battalions, the first of grenadiers, the second of chasseurs. Almost all the soldiers of this regiment are Northern Germans who do not understand the French language. Orders are given in German, and the officers are also German. Their uniform is white with scarlet cuffs, but one also still sees some Prussian uniforms. The grenadier battalion wears red and the chasseur battalion green "Achselbänder" [aiguillettes? - I know nothing about uniforms, that's your domain]; those of the officers are of silver, their cockade is red, white and green. Two days later, the first Irish regiment, about 1200 strong, made its entry. It has its grenadiers, voltigeurs, sappers and excellent music. This beautiful corps wears green short coats and kaskets with large plumes of feathers; on their guidon, surmounted by an eagle, is painted a harp, with the inscription: "L'Empereur des Français à la légion Irlandaise". A few hours before my departure, the 69th Line Regiment moved in; many other troops were still expected, 8000 men were to be quartered in Antwerp itself; six generals had already arrived to command them. At the same time, the naval armaments in the harbour continued uninterrupted. A few days ago, in the presence of an immense crowd, including the Duke of Ahremberg and the Princess of Benevento, wife of Monsieur de Talleyrand, the two ships of the line Duguesclin and Caesar were launched [... the rest of the article does not concern the two regiments any more]."
Perhaps this can help:
https://eudocs.lib.byu.edu/index.php/Historic_German_Newspapers_and_Journals_Online