Gap Insurance for private healthcare policy

Hi, The immigration attorneys I used to make my Residencia application strongly recommended Sanitas private insurance, Mas Salud, without excess, and to be paid monthly on an annual contract. All well and good so far, though not exactly cheap. However, Sanitas have some very long exclusion periods during which that particular medical condition is not eligible for any claims. I haven't compared these exclusion periods with other private healthcare policies, but does anybody know if there is such a thing in Spain as gap insurance to cover these temporary exclusions?