Create a custom editor (inspector) for your scriptable object, then for the sprite collection data / spriteId pair, use something like this:
tk2dSpriteGuiUtility.SpriteSelector( targetSprites[0].Collection, targetSprites[0].spriteId, spriteChangedCallbackInstance, null );
Refer to tk2dSpriteEditor for more details on the additional requirements (spriteChangedCallbackInstance) for this.