Search IM91 pen. It gives you dosage (dosimeter) by 24 hr increments. I'm sure they are everywhere, because they were a staple for soldiers in the cold war era.
Erv
Dosimeter Charger Military Surplus
$65.89 #CDV-750 This is just for the square item in the picture.
IN STOCK
(Purchase pens below) All units Tested & Certified w/Official Testing Equipment - Operational and Reliable
Place the pen in your pocket before you go out into a radioactive zone. When you come back into your shelter record the reading by looking through the pen at a light and writing the number in a log. Keeps track of your exposure. Place the pen in the charger to zero it for the next time you use it. Basic Instuctions , More Info
Dosimeter Pen Only Military Surplus, All units Tested & Certified w/Official Testing Equipment
These units have been Electrical Leak & Rad Tested as Operational and Reliable
#CDV-742 0-200 Roentgens
$45.00/ea
IN STOCK
http://www.survivalunlimited.com/surplus.htm