There used to be an item wanted type of listing, but it was pretty much useless because it generated far more spam than actual matches with the potential buyer's request.
Instead, do a keyword search for what you are looking for in the search box on most main site pages (but not on these "Community" pages). Refine your search by including other words that a seller might use for the item and setting filters to leave out as many non-target items as you can without also leaving out target items.
If you don't find what you need this time, "Save" the search towards the top left and select the option to have eBay email you new listings that meet the search criteria.
