mid size cars need about 14,000 btu/hr capacity to "pull down" the temperature in a reasonably short time. The unit at this link has about 10,000 btu/hr capacity. It's advantage is that full capacity is working even when the car engine is idling. So it might be enough.
Still researching variable speed car ac scroll compressors.
that looks good but at alibabba, they require an order of 40 or more, so though they have some good things, It dont work for do it yourselfers.