Do you know how much troublesome is try to make a toothbrush stay upright on a plane so that bristles don't touch the surface? I try to do that every morning and I still can't do that! So I usually keep my toothbrush in a cup, but it hardly fit into the bathroom cabinet, and it has to be cleaned very often. If you're accustomed to buy always the same toothbrush you can make this useful holder.
You don't need too much tools, but maybe you've to steal in secret your girlfriend toothbrush, wait to trash your last one, or to open another brand new one, so to have two of them. Then of course you need a little package of Sugru. I've used white because is one of the last left ones from the eight coloured mini packs.