Any "loose fitting" hat will do including ball caps. The issue is that the band is not too tight so that it puts tension on your sutures. This is of course if you have strip. As you already know, there are no sutures with FUE because there is no strip excised.
The other issue with both strip and FUE is protecting the recipient area. Again, you do not want any pressure or rubbing on the grafts especially in the 72 hour post-op period.
Some patients prefer the use of a bandana that can be lightly worn over the scalp.
Hope this has been helpful and best wishes to you friend...
Independent Patient Advocate
NOTE: I am not a physician and not employed by any doctor/clinic. My opinions are not medical advice nor are they the opinions of the following supporting physicians: Dr. Glenn Charles, Dr. Jerry Cooley, Dr. James Harris, Dr. Bob True & Dr. Bob Dorin