If the appearance of the gun is not an issue (which I am sure it is) I saw a gun in Rifleshooter magazine where a guy in Alaska used bondo to raise the comb, looked like hell though, but he said it worked and it was "custom fit". Used it for Brown Bear if I recall.
Midway or Zanders use to sell a leather cheekpiece that went over the stock, it was padded, which I am sure was more to prevent the stock from popping your cheek, but it also raised your line of site (i.e. a padded raised comb). I bought a old Enfield that had one on it , they attach pretty easy.
Saw a guy use one of those simple little elastic cartridge holder and he slipped a folded washcloth on the top of the stock to raise his line of site.