Advice on camber / castor gauge - which one

[25th QV]

I'd like to be able to fine tune my camber and castor, and whilst i have a digital angle finder for camber and appreciate there are various ways this can be used with calculations to determine castor, I'd rather purchase a gauge that does it all for me, without my human error - I attach to the wheel, turn it and it give me a castor number.

What gauges have people used and recommend?