If you go with the D cells, be sure to wire in a nice bright LED on one supply to remind you the Bugle is on. I could have bought a Cornet with the 9V batteries I went through forgetting to turn off my Bugle. Finally I switched to 12V SLA's, mounted both batteries and the bugle in a DirectTV box and wired the power LED and Bugle via a 4PDT switch. This setup is convienent but it's probably not any cheaper or easier than buying the power supply.
Gordon