I put the oem suzuki handguards on the other day, and I just checked the install. Instructions to see if the bolt sizes were listed, unfortunately not. The part # on the oem guards is 57300-27820-291. Perhaps more bolt info is available if you use that number. If they'd have just listed the bolt sizes on the install sheet...oh well. Good luck.
57300-27821-291 is the new part number. The picture is for a DL1000 so is a little different. 5 and 11 are representative of the hardware. They are shouldered, with tall hex heads and the heads are tapped to receive screws. You won't find those at a hardware store.