low giraffe, smaller than a nimbus 5 foot. A 5 foot sem would prob be ok. Basically something noticably smaller than a 6 foot sem which is 6ft for a 5 foot 11 bloke. Would buy a new one if such a thing exists.
I got mine from here £60 including shipping
http://www.winstanleysbikes.co.uk/product/24514/Reflex_High_Circus_Chrome_20Inch_Unicycle
Nasher