You read regularly that a reflector is useful and the normal DIY approach is to mount some tin foil onto a piece of card. I found another option that looks a bit more professional. One of those silver reflectors used to keep the sun out of a car window. It's quite thick, flexible and can be cut up into shapes to suite certain subjects. I have two small pieces that I can fold up and carry in my gadget bag and use for close ups such as fungi. I saw another member (Chase) using gold reflective card that you would buy from a stationary shop. This worked well too, but card soon gets shabby, so you will need to replace more often.