What you are looking for is a headphone extension cable. The problem is that what you want is short and extensions tend to be long (6' or more).
If you can find a local repair shop they should be able to replace the plug with one that fits or make a short extension cable for you.
Whether either option makes economic sense will depend on how much the headphones cost you
If you have a case on the phone sometimes trimming it around the headphone jack will solve the problem.
The cable is for home use (from my pc to bluetooth headphones) that i got on ebay for like £3, so you're right in that it would cost more to get the plug replaced unless i bought the materials myself in a hardware shop. I don't trust myself with diy electrical jobs so I definintely won't be doing that.