I'd like to smooth some model prints and chemical is the only practical method (detail too small for sanding).

Are there any ABS or ASA filaments that look silverish like Pla silk? I do want to waste money on another grey spool.

It likely has to do with the print temps. PLA Silk fomilstions have additives that give it the metallic sheen that don't work well above a certain temperature; anyone who's tried to print PLA Silk above 200C could show you how well that works out. ABS can't print below 250c so that additive will be dead.
Also, vapor smoothing someone that has a certain surface appearance after printing will likely lose the surface appearance entirely.

Polymaker sells some "metallic ABS" that is not quite a silk appearance but appears shinier than typical ABS. I'd give them a try maybe.

I'm not sure about your temps, I print all my pla including silks at 220.

results vary, i have some chinese stuff that turns into a mess anywhere north of 205. point still stands the stuff they add to silk won' hold up to ABS temps.