Depends how low you want to go i guess. Just bought my mate this one for his elise:
http://www.machinemart.co.uk/shop/pr...m-trolley-jack

Not the cheapest and not highest capacity (he dont need it) but with the heavy use at least its got some reasonable warranty on it that is likely to be honoured.

A lot of the ebay copies you will be fucked when it breaks in 6 months time.