The strings made especially for Bandolas Llaneras do exist, but are not available everywhere. Therefore, you should substitute other instrument’s strings for bandola strings. The strings for classical guitars fit perfectly. The correspondence of strings between bandola and classical guitar is as follows.
As there are many different kinds of strings available for the acoustic Spanish guitar, do not limit yourself to making use of only these models being mentioned. Find what is most accessible to you and what fits, but do follow the necessary ordering of the strings as is indicated above.