Method 1: Find a cracked list of League accounts any region verified or not 
verified doesn't matter I usually find Lvl.30 lists. hopefully a big list 
( can be a dumped, or a personally cracked list would be best ). now run that list on sentry mba 
checking for PBE (: if those accounts have not been checked before for PBE you should at least get 1-3 PBE accounts easy.
 
Method 2: Grab a freshly posted user:pass SQLi combo dump and go to sentry mba and check for PBE accounts, 
if it's a good combo and you are first to check you could get 10-40 pbe accounts fast and easy (:
 
Method 3: Go purchase a private user:pass SQLi Combo or use SQLi dumper to get your own, then open sentry mba 
and check for PBE accounts. if its a good private combo you will get lots of PBE's, all pretty much unverified and inactive too