Internship after MastersWatch
Judging by your post history, you appear to be aiming for IBD which probably is the least forgiving for lack of experience and recruitment outside the traditional pipeline. I would apply to internships with firms that do not specify penultimate year students, off-cycles for the ones that do, and apply to graduate roles for boutiques and those that do not allow it.
Most firms that allow for summer internship will let you start in their January intake so you will not be left waiting for a year.
I've seen 4th year students get Spring Weeks...