You might like Rav Dovid Feinstein's Seasonings of Torah - weekly divrei Torah based on gematrias. The blurb reads as follows:
Enter the world of deep Torah insights through the eyes of Hagaon Harav David Feinstein. The Rosh Yeshiva of Mesivtha Tifereth Jerusalem, Rabbi Feinstein is one of the most distinguished halachic authorities in this generation. Less known, but of significant grandeur, are his weekly lectures on the parashah that keep scholars and laymen riveted to his words. The Rosh Yeshiva's parashah teachings are enlivened by brilliant conceptions in gematria that go far beyond simple allusions contained in the numerical values of words. Rabbi Feinstein's unique approach elaborates on gematria in the broadest sense: ingenius rearrangements of letters and vowels render meanings never before revealed...
I have never read it, but there is also Rabbi Glazerson's Through the Lens of Gematria
Gematria is a powerful tool for discovering hidden levels of drash, remez and sod of Torah
Gematria is not pshat, the plain meaning of the Torah, but is a powerful tool for discovering hidden levels of drash, remez and sod.
Gematria is one of the Thirty-two Methods by which the Torah is ex- pounded. All of these were given at Siani. They are recorded in the Baraita of the Thirty-two Methods of Rabbi Eliezer the son of Rabbi Yossi HaGelili, which states: “The twenty-ninth method is Gematria.” The Midrash states that Gematria is based on the fact that the order of the letters of the He- brew alphabet – i.e., that is “aleph” the first letter, “bet” is the second, and so on – was one of the laws given at Sinai