Reaching Out Without a Connection

I'm at UCLA, so have been emailing alumni bankers for the past month or so. I am pretty much only targeting SF tech, so somewhat limited in my pool of people to pull from. I've had around a 35% hit rate with analysts (some alumni some just also from the Bay Area) and probably closer to 5% with more senior people like MDs.

Basically my pool of people to contact is dwindling, and I have done nowhere near enough networking. (Between to 15-20 calls total so far). Have had some great ones that led to referrals, but also at a lot of my top banks haven't been able to get anyone on the phone yet.

I'm thinking about emailing people from other LA colleges that ended up in SF, namely USC, but I doubt that will have a high hit rate, and then potentially people from other UCs. Don't really have any other obvious angles to pursue, seen a lot of the common suggestions on the forums, so not totally sure how I should move forward. Is my other UCs/LA schools idea pushing it? Is it even worth emailing someone if there is literally no connection? What would that email even look like?

Any advice on what to do when you hit an alumni wall would be helpful.

Thanks!