SRAM force 11sp brake caliper:

• 2pc 22.4 x 18 x 2.2mm square cross section (piston seal)
• 2pc 8mm x 1.2mm (inner seals)
• 1pc 10mm x 1.0mm (hose arm seal)
• 1pc 5 x 1mm? (bleed port seal)

Brake lever:

• ? piston o-ring seal bottom, top
• ? cable entry seal bottom, top

Piston: 17.85mm (aka 18mm)

Piston seal sources:

• Official seal/piston kit (sram # ..)
• MYA-018 is close
• Stack two 1mm or 1.2mm round (not thick enough)
• Use single ~18 ID x 2.5mm dia round o-ring (not ideal)
• Ebay: https://www.ebay.ca/ulk/usr/pavlina_kyrychova possibly

Different size piston available here (26mm OD) labeled as PE: https://www.aliexpress.com/item/4000509364502.html