I've been on a cold streak too. I couldn't afford all the ones I saw at the start, and now I'm just sitting on a pile of Rift Coins waiting for another good catalyst to show up.
Just got High Waters. Of course now I'm out of rift coins so it's another 7 days until I can use the cabinet again. Check often, and I'm sure eventually you'll get lucky.
I check around 10 times a day. Haven’t seen many in the past two weeks compared to the first week of 3.2 release where I bought about 10 unique ones within a week. That said I just bought the robo Unique today (first purchase in 2 weeks). Seen about 4 hollow-point though..