I was saying (but not suggesting) that you just look at the file chocolateyInstall.ps1 in the chocolatey package, at the link I gave, and use the download URL for Dartium that is in that file.
I am not posting that URL directly because I really think this is a useless and dangerous product to download at this time.
Why can't the app be compiled with dart2js using the 1.24.2 SDK and deployed? Was it really deployed to the web only as .dart files and not compiled with dart2js?
Only the case of a deployed app with deployed dart files, that cannot be redeployed using dart2js, and which must be used in its current deployment, would justify running Dartium.
You may want to post, with more detail, the actual problem you are trying to solve, instead of focusing on this Dartium approach to solving it, which isn't recommended at all.