Have a look at this site - it includes a discography of recordings of the Child ballads. For the Robin Hood ballads, look at numbers 117-154 in particular, although there are some others outside of that range.

Child Ballads Project

Here's a link to one in particular that has a few Robin Hood ballads on it:


Ballads Thrice Twisted

Most of them listed on the above Child ballads site seem to fall under the folk category. It's probably hit or miss whether you can find these in music stores. , but you can probably locate a lot of them online.

If you want to order several miscellaneous ones, (once you locate the specific titles on that site or elsewhere) you could try Elderly Instruments:

Elderly Instruments