Don't think you can fit them without buying a full seat cowl kit from Suzuki. The grab rail holds the rear seat's tongue down. Wihtout it, the rear seat falls off! The Suzuki seat cowl kit has the replecement "Holder" which has the blanking plate holes in it.
See here;
The silver bit is the new holder
with the holes you need.
The bottom of the seat and cowl both have this white plastic affair, the original grab rail, and replacement cowl kit rail hold the lower, middle white bit of plastic down. I can't find a part number, but the Suzuki website lists the cowl kit, if I remember, it's about £45 all in.