Can I add wireless speakers to a conventional audio system?

I have a conventional amp, phono, radio, cd player, wired speakers set-up in my living room. I’d like to have a speaker or two in a room that’s about 40 feet away and not easily reached by running wires to it - to say nothing of avoiding the unsightly-ness of it all. What would I need in order to add wireless speakers to my system? Is it easy? Is it expensive? What are some reasonable approaches to solving this problem?

Mods - I shoulda looked on line before posting this. I didn’t realize I was so far behind the times that there are gazillion types of these things. You can take this thread down.

I almost responded a while ago with a few examples but dinner was calling. I see you’ve found what you’re looking for.