You may go several trips to either place and get nothing, but then get 4-6 bars of eridium in one trip. I would average about 1 bar of eridium per trip to Roland's per visit and maybe average 1 bar for every 2 trips to Scooter's.
At one time, after getting to Sanctuary I would look for eridium in the lockers in Roland's headquarters and in Scooter's, then Save-Quit-Continue and do it again. Borderlands 2 - Slot Machine Tips Borderlands 2 Slot Machine TipsĮridium can be found throughout the game, but not very often and normally only 1-4 bars in any one place.