Are you sure you want a pyrANometer? It measures incident solar radiation. If you want to study (the surfaces and potentially the insides of) solar cookers you might be in need of a pyrometer.
In that case, take one that delivers a sensible temperature range: from ambient to the highest value you expect in the cooker. And get one that provides information on the size of the region the temperature is sampled from.
Best to send an email to Kipp & Zonen, they are one of the top suppliers and would be able to advise on a cost-effective model for solar cooking research