where is custom urf games?

Not available because of a bug. There was a post on it earlier

Yeah, custom games for URF would be awesome.... URF in TT, URF in SR....

the only way to play who you want in URF, gone like . . . I've been waiting for months upon months to play some of these champs, and I can't when it's All Random

that leaves custom, which is by far less satisfying to play but at least- oh wait it's gone

I will assume they have simply locked it for friday/saturdayish. Expect it up saturday-sunday.