If you want to get more reviews for your book, the easiest way is to allow your book to be in the KDP Select program. This can be accomplished by selecting the option in your kdp dashboard. I have heard the complaints, but the fact that Amazon sells more books than any other retailer, both online and offline, makes most complaints moot.
The other way is to purchase a copy yourself and then loan it out. When the review has been posted they can return the loan before the 15 days are over. So, don’t worry that you can only lend it out twice a month. That’ll depend on the loanee to return it early, if they finish early. But, don’t forget to remind them in your note when you send the loan notice that they should return it manually if they finish before the 15-day deadline.
I hope this helps those of you all here who are worried about reviewers having to purchase a copy of your book in order to review it; KDP Select/KU programs or purchase a copy yourself to loan out.