Yes the latest models have constant on/off switches.
These are the model #'s
black bodies
LML-2004 INOVA MICROLIGHT RED
LML-2005 INOVA MICROLIGHT WHITE
LML-2006 INOVA MICROLIGHT GREEN
LML-2007 INOVA MICROLIGHT BLUE
Translucent bodies
LML-2008 TRANSLUCENT RED MICROLIGHT
LML-2009 INOVA TRANSLUCENT WHITE MICROLIGHT
LML-2010 TRANSLUCENT GREEN MICROLIGHT
LML-2011 INOVA TRANSLUCENT BLUE MICROLIGHT
Here's a scan of the catalog page:
http://www.discountknives.com/MicroLight/inova.jpg
The black bodied light have the government NSN numbers (and not the translucent bodies)
However I note at the government spec sheet at:
http://dscp103.dscp.dla.mil/gi/general/lightcat/Inova%20Micro.pdf
these look like the earlier models without constant on/off switches
BUT they have the same models #s.
So check before you buy that they have the constant on/off switch.
I have recently got 3 Inova microlights (all white 1x 2005 and 2x 2009) one of the constant on/off switches was stiff and hard to operate - so samples can vary.
All 3 are noticably bluer than the white Photon 2 I have. One sample was less blue than the other 2 - but still bluer than the Photon.
I am in two minds about which body I prefer.
I like the minimal light leakage of the black body -
but I also like the translucent body for the fact the whole thing lights up so would be great for signaling and attracting attention.
The Inovas look nicer - but for me I prefer the Photon 2 in use.
The lowest price I have found for the Inova Microlight was at
http://www.thenerds.net @ $5.39 each - but their shipping charges are outrageous - you might want to write or phone them and talk them into giving a better shipping rate.
http://www.thenerds.net/productpage.asp?c=74&pn=LML2005&sd=&d=&m=EMISSIVE+ENERGY+CORP%2E
The lowest price on the Photon 2 was $8.75 from
http://www.vicomptel.com/photonlights/Photon2.htm
they will ship for 0.60 per light first class mail....