I am running a rio 1100 I think it is on my remora. Works really really well. The first remora I had I ran with a maxijet 1200 and it also was just fine.
I am not sure where to get the replacement o ring thing, have you looked on ebay? that'd be my best bet I say.
Youll love the remora, I do. In fact I bought my second one recently to run on my 40g after running one on a 29g and 55g. It worked really well on all the tanks.