Lucy, I very sincerely doubt you would find it easy to come across a maltese, let alone a "cheap, affordable" one-and if someone was advertising a "cheap" one, I'd want to know why!! You could try getting in touch with the breed club to get details of rescues, otherwise, try your local shelter, you'll find plenty of affordable dogs in there that require homes! :)
MALTESE CLUB. Sec. Mrs G Franklin. Tel No: 01978 843241