An quick fix would be mounting the reg on a hetsink that s sticking outisde the box.
These linear regs work by thurning the over voltage in to heat.So if you have 100 mA runing trough your reg you would make 0,7W of heat and whith no heatsink this can get realy hot.(Soldering irons have like 10 W)
An good fix would be to replace it whith an switchmode powersuply.These generate very litle heat.Becose the acses voltage is thurned in to amps rather than temperature.A lot of companys make switcmode controler ICs(Maxim,National semi,Microchip,Texas instuments...) Some have the intergrated fet so you just wire up a few resistors,capacitators and an inductor.For more power just use an external fet one and throw in an power MOSFET.
So you decide the ulgy simple quick fix or the slitly more complicated nicer good fix.