I usually take an army1987-type approach in this situation, but here's another possible compromise.

Recently I was flying and wanted to ask someone next to me about the novel they were reading. I waited until half an hour before landing to talk to them, to set a limit on the conversation's length — no implicit request they chat with me for the whole flight. When I did talk to them, I (briefly!) acknowledged the interruption, and kept it specific: "Pardon the intrusion, but what do you think of the novel? I've read some of John Lanchester's nonfiction but I haven't read Capital yet and I've been thinking about picking it up."

Asking a specific question lowers the conversational stakes since someone can just answer the question and then resume what they were doing without violating politeness norms. (That time my question led to a full-blown conversation anyway, but the important thing was giving the other person a chance to gracefully avoid that.)

Things are of course different when you want to improvise small talk instead of asking about a specific thing, but you can still use external circumstances to implicitly limit the conversation's potential length, and ask about something arbitrary as a conversation starter. (This is no doubt a reason English people making small talk stereotypically talk about the weather. English weather's variable enough that there's always a little to say about it, it's a bland topic that won't offend, everyone in England has experience of it, and there are well-known cached responses to weather-related comments, so bringing up the weather doesn't demand much mental effort from other people. And since it's a low-commitment topic it's easy to round off the conversation smoothly, or to make brief, just-polite-enough noncommittal responses to signal an unwillingness to chat.)