I don't know how much you are willing to spend, but there is an SU-10 going for $80 buy it now, and two other ones going for $100 as we speak. You ain't gonna find much cheaper than that.

on the same field, the sp202 is an alterantive but you got also the akai s-20 or the akai remix16...but both don't got with batteries (and the remix16 is real big)...the 2 akai got more or less the same good editing power of the terrible couple su10/ms1 and also the same "fake" sequencer...i could suggest also the yamaha su200 but take a look at the thread on the other machine section (http://sp-forums.com/viewtopic.php?f=11&t=4225) and you will know why i'm not hot about this gear...