What is the part called?

I have a Hoover U3485 upright and I am in need of a part that I cannot find online. The part in question is the foot operated plastic button that has to be depressed to adjust the "upright" part of the Hoover. There is a part within that button that has broken which causes the "upright" part not to be able to lock into the upright position. It simply falls to the floor.

My problem is that I don't know what the part is called and there is no part number stamped on the actual button. The button seems to come with a small spring and a plastic piece that actually locks into the body of the upright, this small broken plastic piece has >POM< 2/2 stamped on it and seems to have a piece broken off and missing from it. Ideally this is the piece I need and I assume it may all come together with the button assembly, but not sure.

If someone could let me know either a price for this part and/or what it is called or possibly a part number it would help. I would like to fix this ASAP as it makes using the Hoover very cumbersome.

Thanks,
Dan