As far as I know, there is no single updated centralized database for undergraduate philosophy journals. PhilEvents has the ability to search only for student journal calls for papers, but many student journals sadly do not submit their call for papers to PhilEvents, and the search also includes graduate student conferences which are not relevant for undergraduates.
So, I've made a list of undergraduate philosophy journals. Rather, I have made a list of lists, with appended entries that do not appear on the other lists. I will try to keep this list up to date. If you know of a journal (or a list) that belongs on this list, please get in touch with me so I can add it to the list! Or, better yet, add the CFP to PhilEvents and save me a bit of work. Students interested in whether to bother should read this.