Per Coffee 97' Parts Diagram / List ER0077/01
DM0041/082 OR 167 gasket EPDM 70 SH - O-Ring between boiler and group body
This is a 2 3/4" OD - 2 1/2" ID - 1/8" W Material: EPDM Durometer Hardness: 70A - AS568A Dash Number: 230
A pack of 25 is available at Small Parts for $6.96
DM0041/022 OR 2025 gasket red - O-Ring between inlet fitting and group body & between group valve assembly and group body
This is a 3/8" OD - 1/4" ID - 1/16" W Material: Silicone / VMQ Durometer Hardness: 70A - AS568A Dash Number: 010
A pack of 100 is available at Small Parts for $11.07
DM0041/081 OR 112 gasket EPDM 70 SH - Seal between steam valve and boiler
This is a 9/16" OD - 3/8" ID - 3/32" W Material: EPDM Durometer Hardness: 70A - AS568A Dash Number: 110
A pack of 100 is available at Small Parts for $3.68
or if tolerances are "loose" - big
This is a 5/8" OD - 3/8" ID - 1/8" W Material: EPDM Durometer Hardness: 70A - AS568A Dash Number: 204
A pack of 100 is available at Small Parts for $5.65
DM0041/088 OR 2025 gasket - O-Ring between steam pipe - lower pipe and steam pipe - uppper pipe
This is a 3/8" OD - 1/4" ID - 1/16" W Material: EPDM Durometer Hardness: 70A - AS568A Dash Number: 010
A pack of 100 is available at Small Parts for $4.34
Group Gasket NG01/001 - Mine is 8.5mm thick 57mm ID 72mm OD
Tex at the Gaggia Users Group recommended I use a $6.06 E-61 Soft 8.5mm Group Head Gasket from Espresso Parts.
Last item on the list is 4 DM0701 Belt - Spring clips to secure latex tubing.
Still Researching but these may work:
Acetal Snapper Type Hose Clamp, Quick Ratchet Closure, For 3/8" Nominal Tube OD, .351-.394 Clamp ID (Pack of 10) $4.55 at Small Parts
These are plastic so they will not rust like the original ones did.
This is a helpful o-ring sizing chart
A potentially sleep inducing 256 page technical handbook on o-rings - could be handy