There is another option:

Enroll in the Sports Officials Insurance Plan for ASA Umpires. Bollinger Insurance started this in 2003. For $15 per year, per umpire, they can obtain this insurance plan. With this plan, an ASA umpire will also have coverage for High School, Junior College and College Softball. Plus, if all you do is ASA softball, this plan will give you game fee reimbursement coverage.

This plan is only offered to ASA Umpires Associations (can't be purchased individually).

IMHO, great deal for all ASA umpires. And cheaper than NASO (I think).