Good plan!

Have you seen these?

http://www.dealextreme.com/p/soshine-2xaa-to-d-size-cell-battery-converter-case-2-pack-7031?item=34

There are several similar designs that accept 3 or 4 AA cells in a D form factor. Even the simple ones for a single AA would allow you to use an AA cell to get your D equipment working (for a shorter time, of course).

Watch out- some designs are series, which means the 3 AA cells are connected together to give 4.5V, which is probably not what you want.