I don't believe there is. I use 2 stroke mix and stainless wire wool pot scrubbers, the oil and petrol appear to soften it better than just petrol alone. Before using the stainless I will run a sharp chisel or a Stanley Blade laid flat (not in the tool) and sliced back and forth using my fingers to hold it on the chamfered sides. This is all learned from bitter experience renovating old windows.
If you take piece of acrylic, about the size of a paint scraper, and put an edge on it (around 45 degrees) you can use it as a scraper. Its too soft to mark the gelcoat (though might depend on the gelcoat?), but tough enough to 'get at' the sika, or silicone. It loses its edge quite quickly, so you either need to re-sharpen or have a few ready. Source, any one using acrylic for windows etc. Ask if you can have some scrap. They need to be big enough to fit your hand but the cutting edge should not be too big (takes more effort).
I once rang Sika themselves to ask this very question. The reply - if there was something to dissolve the Sikaflex, it would also dissolve whatever the Sikaflex was stuck to!