I wish I knew what Honda used on the polished covers. Worked well for a long time. But, it probably doesn't matter. I doubt the governments federal or state EPA guidelines would allow you to obtain it anyway. It's important to note that Honda's covers weren't highly polished for a reason. They were satin or brushed finished because those surface conditions allowed the coating to grab onto the surface. Putting an organic coating such as paint over a highly polished surface often results in failure as the coating comes off in sheets.
Leaving the polished aluminum without a coating means that you will have to re-polish in the future. The frequency of the polishing effort will depend and the atmosphere the surface is exposed to and the alloy composition of the aluminum, in particular, the copper content. A dry, cool climate will increase the polished surface longevity. Warm, humid climates cause rapid dulling and the need for repeat treatments. Atmospheric impurities also have a negative effect on maintaining surface polish. If you have acid rain, ocean salt spray, or airborne chlorine from a nearby pool or water treatment facility, you can expect surface dulling to occur at a faster rate.
The squiggly line corrosion, to which Rookster refers, is called filiform corrosion. It occurs under coatings that have had poor surface prep, and/or microscopic coating pores where atmospheric contamination and humidity have reached the aluminum alloy underbase. It is not generic to a clearcoat, but can certainly occur with such a coating.
If you can still get clear lacquer where you live, I can definitely advise against its use. It will yellow with age and stands up poorly to the sun's UV light spectrum.
Cheers,
