Long story short - I have a Breville Bambino Plus and am trying to add the water filter. The Breville machine is sold without a filter, while the Sage variant does have it. Breville sells the filter separately, but they do not sell the small adapter ring that is required to attach it. I am hoping someone with a Sage Bambino or Bambino Plus would be so kind as to remove the adapter ring and take some photos and/or measurements of it, so I can make a 3d printed replacement.

I believe the adapter ring is the same as used on other models like the Barista Express, etc. I think any that use the 'Claro Swiss' filter.

My recommendation would be to just use bottled or mixed water than is known to be reasonably "scale-free". The in-tank filters (in general) require long contact time to be effective and "effective" can be fuzzy as to what the filters do. Many popular drinking water filters do little for reducing the minerals that can cause scale. Certain bottled waters have appropriately low mineral content. Mix-your-own can be done with RO, deionized or distilled water (including, for example, a ZeroWater filter). Some of the recipes are very easy, requiring only one common ingredient. See the Water section for more information.

I would not use a 3D printed part as they are not food safe. Even if the plastic is suitable for food contact, the gaps make printed parts unsuitable.

Thanks for the input. However, I am absolutely not willing to use bottled water. It is frankly shocking to me how accepted this is within the espresso community. I understand the benefits, but it is just not something I will do.

I also am aware of the issue with 3d printed parts, however it has minimal contact with the actual water, and will be coated with food safe epoxy resin.

You might have more response on a UK or Australian coffee forum. You'll also be able to get the part from UK or Australian parts places - but not every parts place will ship to Canada.

Note that the in-reservoir filter will not remove chloramine, which is widely used by municipalities in Canada for water treatment.