You can share one with someone else in your circle, or you may be able to borrow a loaner (slightly used discussion guide, donated). In either case, you can download blank evaluation forms and the blank worksheets included in the discussion guides. Choose the guide you have and find links to these documents on the right-hand column.
You can ask the SMEI point of contact in your neighborhood whether someone has donated a discussion guide you can use.
Ideally the loaner guide should have the same year of publication as the current text, listed here. If it's different, be prepared to encounter differences between what you read and what other group members will have read prior to discussion. Sometimes the differences are significant, sometimes very minor.
If you've just finished a circle and no longer wish to keep your discussion guide, please give it to the mentor at the Wrap-Up session, or get in touch with SMEI volunteers in your neighborhood.
If you have an older NWEI guide that you no longer wish to keep, don't throw it out! Leave it in a place that collects used books, for others to browse.
Ultimately, please recycle your used guide instead of sending it to the landfill.