Go into chat and type "/bonus" (without the quotes). All bonus weapons will be added to your inventory. Drag the ones you don't want right now to the trash. (You can always get them back again by typing /bonus.)
Also, typing /bonus only works while in an outpost. Make sure you have enough room in your inventory as well, otherwise it'll only spawn as many weapons as there is room.
You can get additional copies of them by equiping the bonus weapons on your heroes, before typing /bonus again.
