Since the 1970s, the president's pen have/had been made by A.T. Cross. Bush Sr. through Obama all used the Townsend, though Obama later switched to the Century II. Trump is not a fan of the pens.

https://www.pens.com/blog/presidential-signatures-and-signing-pens/

Trump will use one every now and then, but it turns out that his pen is custom made by Sharpie.

https://www.businessinsider.com/trump-uses-personalized-sharpie-pen-2018-11

“I was signing documents with a very expensive pen and it didn’t write well,” Mr. Trump said on an HBO special produced by the political website Axios. “It was a horrible pen, and it was extremely expensive. A government-ordered pen.” He said that he had pulled out a standard Sharpie pen and concluded that it not only “writes much better,” but also “costs almost nothing.”

“So, I called up the folks at Sharpie and I said, ‘Do me a favor, can you make the pen in black? Make it look rich?’” he said. 

You may remember "sharpiegate". Custom, Trump "Presidential Collection: Signature Edition" Sharpie Pens.

https://www.nytimes.com/2019/09/05/us/politics/trump-sharpie.html

Now why was it a horrible pen? What was he really saying about the pens or their previous owners? What documents were signed by President Trump with A.T. Cross pens? Can we get a list of those documents?

A. T. Cross website: https://www.cross.com/cr_en_us