A WorldCat link (subscription required) may be found here (Staff and students of Groningen log in with p- or s-number).
This is absolutely the first place to go to find new inscriptions – and to find later editions, comments etc. on existing editions.
Supplementum Epigraphicum Graecum (SEG) is an annual survey, collecting newly published Greek inscriptions and studies of previously known documents. New texts are normally reproduced with a critical apparatus, and brief comments. Texts that are published in epigraphical corpora repertoria are not normally reproduced in their entirety.
Each issue contains the harvest of a single year, with a delay of a few years: for example, the most recent issue of SEG (2021 vol. 66) contained all inscriptions published in 2016. SEG covers the entire Greek world, but material later than the 8th century A.D. is not included. The texts are arranged geographically according to the order of Inscriptiones Graecae. After that follow Asia Minor, Syria, Palestina, Arabia, Egypt, Nubia, and Kyrenaika, with the cities listed in alphabetic order. For each place the texts are listed in chronological order, according to 4 categories: public documents, dedications, epitaphs, miscellaneous. Inscriptions with an unknown provenance are discussed separately. A very useful section Varia discusses epigraphic bibliography on various topics.
The volumes have extensive and excellent Indices: Names of men and Women, Kings and dynasts, Roman emperors, Geographical Names incl. Attic tribes, demes etc.; Religious Terms; Military Terms; Important Greek words; Selected topics (Eglish); Concordances to IG and other major corpora and SEG volumes, as well as a list of abbreviations. There are also separate index volumes available.
The current editors of SEG are: A. Chaniotis, T. Corsten, N. Papazakardas and E. Stavrianopoulou.
Online versions
SEG is available online via Brill scholarly editions. It offers extensive search possibilities. instructions for the search possibilities can be found here. Indexes can be found here. Search options are not always intuitive, so you may need to practice.