[JT118]

http://www.metspec.net/unaspirated-radiation-shields

These are about the best, and manufacture the campbell scientific shields you mention. The davis shields are also good,

http://www.davisnet.com/support/radiation-shield-7714/
http://www.ebay.co.uk/itm/DAVIS-RADIATIO...SwLzdWTI-y
http://www.davisnet.com/support/fan-aspi...on-shield/

http://www.davisnet.com/support/solar-po...ield-7755/
http://www.ebay.co.uk/itm/DAVIS-VANTAGE-...SwyQtVv1Od

Cheaper,
http://www.ambientweather.com/amwesrpatean.html
http://www.ebay.co.uk/itm/Ambient-Weathe...SwyDxXhTd2
And very cheap:
http://www.ebay.co.uk/itm/plastic-outer-...SwhcJWH1Or


For other info,

http://www.wxqa.com/shields.html