You are looking for what ATTWS calls a "multi-network"
phone. They have offered two--I'll let you check
and see what current plans go with them. You might
find one if you ask around the neighborhood stores,
or used from eBay.

The Siemens S46 has 900/1900 MHz GSM and 800/1900
MHz TDMA (same "digital" as your D1R plan). This
the one with no 800 MHz AMPS (analog).

The Sony Ericsson T62u is a GAIT phone, and has
800 MHz AMPS. It also has TDMA and GSM on both
North American bands 800 and 1900 MHz.

When you say "tri-band phone", you indicate that
you're interested in a GSM-only phone. Two examples
are the Sony Ericsson 610 with 900/1800/1900 MHz,
and the SE 616 with 800/1800/1900 MHz. The former
would be good abroad with two international bands;
the latter would be good in at home with two
North American bands.

I hope that's enough to get you started.

John C.