Non-spammy Looking Content Locker?

I have a large following via social media + on various pages and groups I own. They all know me well and trust me. I want to give away some eBooks and was thinking of using a content locker to monetize them, but most content lockers I run across seem to be very very spammy looking.

Can anyone recommend something that doesn't look ultra-spammy?

Ideally it would just be a survey they have to fill out that takes like 20 seconds - 1 minute to do, like on news websites.

I looked into CPA Grip and it looks pretty spammy to me.

Well any giveaway you do which asks for unlocking will look spammy. I know this isn't how I'd market anything to my friends.

I know exactly what you mean. The content lockers out there look like something from 10 years ago.

I've been impressed by the look of ogmobi lockers, but they only handle mobile traffic. You could redirect mobile traffic to their locker. For desktop, I've been thinking of Mighty Content Locker (self hosted). It says that you can upload your own css designs. It's not responsive, but if you're redirecting mobile traffic anyway...

Has anyone tried Google Surveys?