Flanders Field Tours

Do you mean just the American Cemetery near Waregem, or the WWI battlefield sites that are mostly clustered around Ypres? If the former, then you could do that independently with a car in less than a half day. If the latter it could take several days to visit all the battlefield sites, memorials, cemeteries and museums. Can't recommend a tour, as we did this independently. But the usual 3rd party sites (Viator, GetYourGuide) list Flanders battle tours.

I did this with a RS Belgium and Holland tour, so no tour company to recommend but if you do it on your own, I'd surely go the American Cemetery if you are from the US. The care the Battle Monuments Commission takes for the cemeteries is just awesome. I also recommend seeing the Commonwealth graves at Tyne Cot and a visit to the German Cemetery at Langemark.

https://en.wikipedia.org/wiki/Langemark_German_war_cemetery

https://en.wikipedia.org/wiki/Tyne_Cot

We were also taken to a location where you could access some of the remaining trenches which was very interesting. It is open to the public as there were some school tours the afternoon we went but I do not know the name of it, sorry.

IF you have a full day to spend on this, I would. Very poignant.

I can recommend this company:
https://www.2xplore.be/

The guide is a former para commando in the Belgian army and very knowledgable on the subject.

If you have a car you might want to check out this open air museum. It gives an idea on what the defence line of the Germans was along the Belgian coast.
Atlantikwall

From Brugges we went on Quasimodo’s Flanders Fields tour. We got picked up at our hotel about 8am and dropped off about 5pm. That was in 2018.