Anyone know of good 3AA to D-cell adapter/converter?

Could something from OSHPark and a few nylon rods work for this?

Another option (5pcs.) http://www.newestrend.com/3-x-aa-to-d-type-battery-adaptor-in-parallel-5-pcs-p-925.html

WarHawk-AVG;

Possible but cheap enough per unit that with materials cost plus your time I question whether worth it.

antiparanoico;

Same things except for plastic color so far as I can see. A bit less expensive but W/O the eBay customer support/guarantee. Either one appears to be a bargain. Yours a much better buy if don’t need so many.

You have to purchase a lot of 10 from Aliexpress:

http://www.aliexpress.com/item/Free-Shipping-10pcs-lot-3-AA-TO-D-adapter-Battery-holder-ROSH/927279612.html

$11.64 for 10

I bought 2x10 of these a while ago:

$20 for 10 and free shipping. Not certain they are the best for high drain applications, but they work very fine for my purposes.

I also bought a bunch of IKEA LADDA nimh AA and replaced all old D-cells in radios, old flaslights and other stuff.