The link is constructcollection.com but you have to pay a lot of money for that and we are already paying the construct 3 license....
Mobile IAP should work within Construct 3 and we should not buy other products or libraries to have something that C3 said it has.
At least, this is my opinion. I know Mobile IAP is not working, but they should carefully look at it as it is an issue on production environment. It would be a minor issue if the problem would be in development environment, but it is not the case.
20$ is not that much, but I'll wait few more days, maybe construct team do something.