Is there a bookmarklet I can use for the Lobsters site?
Yes, there is – it’s “Submit to Lobsters” on the Submit Story page.
To be able to easily submit a page you’re viewing in your browser to Lobsters, drag the bookmarklet to the right to your bookmark bar. You’ll be taken to this page with the viewed page’s URL and title.
window.location = "https://lobste.rs/stories/new?url=" + encodeURIComponent(document.location) +
"&title=" + encodeURIComponent(document.title)
I don’t know of one offhand, but it looks like supplying a url query param to the submit story page does the right thing, so it should be easy enough to write one. You’d want it to take the current window.location.href, URL-escape it & append to https://lobste.rs/stories/new?url=. (Presumably opening it in a new window?)