Looking to clear coat wood over oil-based paint pen

I've basically finished building a lap steel guitar through the guide at http://www.buildyourguitar.com with one change. To save some money and avoid having to clamp/plane the "fretboard" wood, I'm just going to paint the fretbaord directly onto the body, like some of the cheaper lap steels out there have.

I think the easiest way to paint thin lines for fret markers is to just draw it on with an oil-based paint marker, like these from Sharpie.

I'm thinking if I then try to cover the painted body with Danish Oil (or any oil based topcoat), as the guide suggests, the Danish Oil is just going to obliterate the markings made by the marker. Is there a sealant I can use over the oil-based markers that will allow me to finish the wood but also keep the artwork intact? The rest of the body will not be painted, just natural finish. Doesn't really matter to me if the clear coat solution is crystal clear, or tinted.

Thanks all.