reply to u/FriendlyAd4234 at https://www.reddit.com/r/typewriters/comments/1cn004l/olympia_sg1_dust_cover/
Other than the traditional fabric-like dust covers, you might consider doing a thicker plastic/acrylic cover, particularly if you've got several machines and are using them for display purposes. I live in Los Angeles and there are half a dozen places that do this sort of custom work all the time for very reasonable rates. Searching for "plastic fabricator memoriabilia case" along with variations of plastics (acrylic, lucite, plexiglass) should get you what you want locally. (Here's a few examples I've used in Los Angeles before to give you an idea: https://solterplastics.com/, https://www.plasticfactoryinc.com/, https://www.customacrylicproducts.com/, https://plexidisplays.com/). Search for something similar in your area for easier communication and pick up/shipping.
If you search around for companies that make plastic displays, particularly for memorabilia (baseball bats, baseball cards, etc.), you can have them design and make a custom sized clear plastic box/enclosure that will keep the dust and dirt out, but still allow you to see the machine inside.
Levenger index card bleacher for compactly displaying index cards in an array on a desk so that portions are visible but that they don't take up space.