I honestly think any cheap kind of headphones will do, but make sure it's a headphone and not earbuds. Not only can earbuds ruin your hearing over time, headphones are more capable of blocking outside noise, which would be perfect for a transcription job.
I've had a headphone gifted to me a few years back and it did a good job blocking out sound. I should have the box somewhere along and I'll see if I can provide a price tag. Wasn't really expensive, since it was only a Christmas gift, we always give cheap gifts on that day.