Since Music scores for solo harp can be found in a number of locations it is best to use 'Advanced Search' on the Library search as follows:
Subject = harp and Material type = Scores
You can then refine by selecting Online scores or scores Available in the library on Level 1.
P780 DU is a good place to start browsing as this section arranges music for solo harp alphabetically by composer.
For example, Benjamin Britten's Suite Op, 83 is at P780 DU B862 SUI and The Elements by Mary Doumany is at P780 DU D738 ELE
In the S780-SEF780 sequences harp music is shelved under the number 9 for all composers who have composed for solo harp.
For example,
S787.9 is where the books related to harp instruction are shelved.
Online scores take you to the database Classical Scores Library where you can browse over 190 works for harp and select any for downloading.