Usually large numbers of both breeds at Builth and also at the Coloured Sheep Sale at Llandovery but that isn't until September.
This isn't usually the best of times to buy pure bred sheep. Do you want top quality registered stock? Are you looking for mature ewes or lambs?
Balwens can be flighty and the regulations for registering them are to my mind an absolute nightmare. The markings have to be spot on.
Balwen Welsh Mountain Sheep Society is at
http://www.balwensheepsociety.com/Badger Faced Society is at
http://www.badgerfacesheep.co.uk/There is at least one person breeding top quality Badger Faced who is a member of this forum. For more run of the mill sheep I know several people breeding Badger Faced, mainly in Carmarthenshire, and one of those also has Balwens. They might well have ewes with lambs at foot in the spring. The breed societies will also have details of people with sheep available.
One thought is the Smallholders Show. That is I think on 19th and 20th May and there will be sheep a plenty to see and breeders to talk to there. Check the dates on the Royal Welsh website please as I am running out of time and need to go and feed my crowd.
And good luck - yell if you need any more.