I finally had an opportunity to order replacement bp.
Hey, Zoran, I just got mine today. When I spoke with Powerhouse earlier this week, it sounded like they were initially looking at a 130mm (5.12") bp, but a larger one is on order from Germany at 140mm (5.51"). They had about 7 or so of the smaller one in stock and that's the one I ordered. Should work out nicely with 5.5" pads. Heck, I'll probably order the 5.51" one as well when it's available just to have a spare/backup. This machine is definitely picking up some interest as several others have ordered it / will be ordering on that other detailing forum.