To share a link to any particular ad/listing, click on the black bar (date and/or time) to the left of the ad/listing. Doing this will separate the post from the rest of the list. Copy the URL from the top of your page and paste it wherever you want to share it. Sorry to make you jump through so many hoops, but this particular Tumblr format doesn’t accept ‘share’ widgets.
(close this window to return to the listing)