Is there a resource where we can search kanji with the same Onyomi?

The Semantic-Phonetic Script includes a section for each kanji which highlight on’yomi similarities and phonetic components of kanji, right here on WaniKani! If you want an organized resource of kanji and their phonetic similarities, check out this MA thesis paper which has a large chart of phonetically related kanji starting at page 37. It’s also an interesting read, if you’ve got some time.