As I frequently find myself saying, lamp limiters work just as well at DC
In lieu of a current-limited bench PSU, just put a suitable lamp in series. Automotive bulbs are available in a wide range of powers - something like 5W would be as high as I'd want to go for a transistor radio (1 or 2 watts would be better) - and the holders are readily found (or just solder wires directly to them). They also double up as a handy dummy load for testing power supplies, etc.
