My mom wants an earbud style headset for a landline cordless phone but...

Does ANYONE make a good one anymore? Or, barring that, does anyone make a good adapter (3.5 mm female to 2.5 mm male) that actually works to transmit the audio signal both ways–so that you could connect, say, a set of Apple Earpods with built in mic.? I’m seeing some adapters on Amazon where the reviews complain that there is no mic functionality.

She doesn’t want anything with a headpiece. She wants a wired earbud type thing with the mic that just hangs down like for some older pre-smart cell phones and for landline cordless ones.

If budget isn’t absolutely paramount, I’d suggest contacting Headphone.com directly and bouncing a few questions off of them. They have been amazingly helpful to me with personal queries in the past and they’ve always been happy to talk to me on the phone for free. In Ear Headphones, contact form/number.

The Plantronics mx200 looks pretty good.

If you want an adapter, you could just make your own. Start with something like this for the headphone to go into:
http://www.digikey.com/product-detail/en/cui-inc/SJ5-43502PM/CP5-43502PM-ND/1956558

Or if you want the headphone jack to look a little nicer, you can get this one from a different store.
http://www.mouser.com/ProductDetail/Kobiconn/161-6435-EX/?qs=sGAEpiMZZMv0W4pxf2HiV2oxafp8PWP3YPhhB87dh5U%3D

And attach it to a preassembled 2.5mm cable like one of these, and make sure to figure out if the phone has a 3 or 4-contact jack.
http://www.digikey.com/short/3rhfzw

(Digikey didn’t have a 4-connector in-line 3.5mm jack, and Mouser didn’t have an affordable 2.5mm cable)

Thanks for the replies. Actually @corkeh I did end up going with the Verizon-branded mx200, https://smile.amazon.com/gp/product/B0071MGS7O/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1 , which came with an adapter in the box for a handset that only takes 2.5mm jacks (Is “jack” the male or the female, I can’t remember).

The only issue is that the adapter looks super-fragile. The headset’s direct-wired plug is a 3.55mm male and is elbowed. Problem is, the adapter consists of the female 3.5mm jack on a straight connector, a super thin little 1 inch or so cable that looks like it’s already kinking where connected to the straight part. The thin cable connects on the other end to an elbowed 2.5mm jack. So two elbows total in the mix, which is annoying. I urged my mom to wrap electrical tape around and maybe use a toothpick to reinforce the little wire, which otherwise looks like it’ll stop working if you breathe on it too hard.