Id call orange cheeked waxbills fairly common - Im in pennsylvania, and our local superpets, petsmart, and independent pet shot have them right now -
I think there inexpensive too, around 24$ each -
Mineral blocks...hmm - I use cuttle bones and a powdered vitamin supplement added to thier food - I don't know if little birds like finch would try to go at the big supplements made for parrots that you see for sale - you could try getting one and cutting it into a smaller piece, and see if they are interested in that ? or maybe a parakeet block ? Ive never tried either of them -
Waxbills do benifit from the addition to small livefood, and plenty of greens in thier diets, though -
Raven -