I don't know specifics about Riverside fraternities. And more specific, the ones that might meet your needs. As such, your best bet is to contact a current student or alumni, or the Greek Life Office. For what it is worth, it seems that their website
www.gogreekatucr.com/ is no longer active. As such, contact the Greek Life Office (or what ever it might be called) might be the way to go regarding information.
These are the fraternities listed for UC Riverside according to the
Student Life Organizations page.
Alpha Epsilon Pi
Alpha Phi Alpha
Alpha Tau Omega
Beta Chi Theta
Beta Upsilon Delta
Delta Tau Delta
Epsilon Iota Sigma Colony
Kappa Alpha Psi
Lambda Chi Alpha
Lambda Theta Phi
Lambda Sigma Upsilon
Nu Alpha Kappa
Phi Gamma Delta
Phi Kappa Psi
Pi Delta Psi
Pi Kappa Alpha
Sigma Phi Epsilon
Zeta Phi Rho
Best of luck.