are there any bands/attachments to the watch bands that are for motion sickness?

There might be some such compatible bands available from other vendors but not by Apple directly.

There is the Reduce Motion setting that you can enable in any case, from under Accessibility. Then maybe a still clock face could help some too.

Finally I came across this Sense Relief app - have not tried it myself yet:

https://apps.apple.com/us/app/sense-relief/id1457764420