Timin Light Recommendations for +ve Gnd

I want to get a timing light that can be used for both -ve gnd vehicles, like my car, and also +ve gnd, like my Commando.
Any recommendations?

You mean a strobe light?
As far as I know, it doesn't matter which ground it is, they come with 2 leads attached, 1 - & 1 +.

Agree, when using a stobe for timing the Norton I take the power from my car's battery rather than from the Norton's battery. Red lead to positive, black lead to negative, induction lead clips around one plug high tension lead (doesn't matter which, but left side is most convenient since the timing mark is that side).

I use a National battery powered timing light. You don't need to power it from the vehicle and they are as cheap as chips, also useful for vehicles where the battery is in the front but the engine in the rear etc. They don't have any adjustable advance dial but otherwise do the trick.

Timimg lights, or any electrical device cares not which polarity is ground, only that it receives the correct polarity.

Agreed, although to emphasize, I have always understood it to be preferable to use a power source for the timing light separate from the charging system of the vehicle being timed. I have a couple old batteries I keep charged for such purposes. Since I have EI on all my bikes, they don't see a lot of use. Anyone in the Boston, MA area want a free battery? I can probably help you out.