I know the Best Electronics page isn't really user friendly, but they have what you need, no real need to hunt elsewhere in my opinion, unless you don't want to pay what they are asking.
Just send them an email:
Page 143 1020 Platen Motor Unit FC100371 Sold Out
1020 Head Motor Unit FC100370 Sold Out
1020 Printer Mechanism CB101170 Sold Out
1020 Small gear set (2) for the Platen and Head Motors CB101727 $15.00 Limit of 2 sets per customer
Page 148 Atari 820 40 Column Printer Paper roll. CB101922 $5.95 Limit 1
Atari 820 Ribbon CO14854 $7.95 Limit 1
Atari 1020 BX4204 Color Pen Set (4 pens per set) $3.00 New Limit 10 sets per customer
Atari 1020 BX4206 Black Pen Set (4 pens per set) $3.00
Atari 1020 Plotter paper roll set (2 Rolls per package) These are the original Japanese Alps (the manufacture who made the Atari 1020 internal printer mech.) made 1020 printer rolls with the very smooth surface and bright white color. Be aware of generic after market 1020 printer replacement paper with a rough surface and very off white/ light brown color. Generic replacement 1020 paper not made Alps, does not print with the same quality as the OEM Alps made 1020 paper. CO61533 $6.50 Limit of 1 Pack per customer
It appears they have increased their limit on color pen sets which is cool!