This answer already describes the name of the "golden" component you are after, this answer expands upon that answer to note that there are various nuts with different thread sizes that look virtually the same, it would be a pity to order the incorrect one.
Note that this trapezoidal lead screw nut is made from brass (e.i. in your image, but these nuts are also available in POM/Delrin) and needs to have exactly the same screw threads as your lead screw has. A much used lead screw is using the following designation
Tr8x8(p2) ( for a full description of what that means look into this answer (Anet A8 lead screw threads)). Do note that there are many lead screw nut sizes, buying the wrong one will not fit the current lead screw.
From the image you supplied it looks as if that is the same lead screw as used in the linked answer of the Anet A8 lead screw. To verify this, you could measure how much the nut advances on a full rotation of the nut, if it is 8 mm, buy the
Tr8x8(p2) if e.g. 4 mm, buy the
Tr8x4(p2). Note that if you are going to buy a new nut, you could opt for a nut that has no backlash, BUT, be sure that it would fit the acrylic hole and you have enough space as its height is larger, or be prepared to modify the acrylic part or reconstruct a new one (it wouldn't be a bad idea to do that anyways, acrylic is known for cracking under applying force such as screws and nuts). Note that an anti backlash nut must be used as depicted below.