COLD email 20 of them and offer to pay THEM to use your
product if they are willing to offer some feedback.
If anybody responds, tell them that the offer is oversubscribed and that it is no longer available.
I wonder what is wrong with saying just "Hi, I would like to get feedback about project X.". Would that way have the same affect?
I'm asking that just becasue I try to follow an old proverb (not sure if translation to English is correct): if you have a smallest doubt about whether to lie or not, don't lie.
(no, I'm not good with the above rule, but at least helped me while dating and now in marriage)