I got them on Amazon:
Odec D Cell Rechargeable Battery, 2-Pack 10000mAh Deep Cycle NiMH Battery
and,
Tenergy D Size 10,000mAh High Capacity High Rate NiMH Rechargeable Batteries

Of the two, the Odec are lower self-discharge and will eventually replace the Tenergy's. The primary reason to get them was to save Maglites from alkaline batteries.

I'm using a Tenergy charger which has four independent bays which can accommodate AAA-D cells. I'm sure there are better chargers but it's what I bought a few years back. Looking at the specs of the T-9688 Super Universal LCD Battery Charger and Tenergy Advanced Universal Charger TN190 , they're only spec'd up to 9000mAh for D cells. That may be why mine never finishes charging the D cells. The Maha PowerEx MH-C808M Charger is rated for 11,000 mAh.