Is there a way to wait for a callback to finish without using tasks (for obvious reasons)? I'm wanting to return the response, but due to it being async, I can't wait for the webrequest to complete.

//... 
string res = ""; 
webrequest.Enqueue("https://google.com", "", (code, response) =>
{
    res = response;
}, this);
//...

No, it doesn’t support that, but you could use an action for callback. Take a look at my Babel Chat plugin for an example.

Are there any alternatives then?

No, the only thing you could use is an Action like what the plugin above utilized along with web requests.