spice for looking up doi’s

I’d tried to implement https://duckduckhack.uservoice.com/forums/5168-plugins/suggestions/3552182-show-bibliographic-data-when-a-doi-is-entered-

There are two issues where I need a bit help
 * The better data provider requires the "Accept" header to be set appropriately to return JSON data, see http://crosscite.org/cn/ for details. I could not figure out how to configure that.
 * When the web service returns 404, the data is still returned as such to the client. Shouldn’t the proxy handle that more graceful? Is that related to wrap_jsonp_callback?

Thanks,
Joachim