A family of Microsoft word processing software products for creating web, email, and print documents.
There is a Unicode character đwith the character number hex 0111. It's present in most fonts that contain more than just the 128 ASCII characters, such as Cambria Math, Times New Roman, and Arial Unicode. To insert it, you can use the Insert > Symbol > More Symbols dialog, or just type the number 0111 in the document and immediately press Alt+X.
In regular text you can apply italic formatting to the character. In an equation control, unfortunately, I don't see any way to italicize it to match the ħ character.