I used to use batteries to power-up my projects. Not very convenient but it worked quite well.
I builded then power supply myself. I used old laptop charger and aluminium wlan box from dumpster, cost 0 euro. I added voltage regulator, potetiometer and 4 banana terminals, cost few euros. It can give 1V - 18V 4A output. I might add later current regulation, but I am quite happy with it already now.