Hi Digger,
the ppO2 housing is a piece of clear polycarb tubing. On each end are a couple of delrin caps with o-ring seals. On one end cap is a cable gland for connection to the sensors. On the other is a removable plug (like a reg blanking plug)to allow for calibrating the display. One end cap needs to be removable to allow for changing the battery. The other end cap can be glued in place.
If you have access to a lathe then you can make up a housing very cheaply. If not then find someone abroad to do it, it costs a bomb to get anything machined here, that isn't even counting materials. The stuff I'm getting done for my new RB is being done in the US, Poland and Switzerland for a fraction of the price. It was just too much to get a UK machine shop to do the work I wanted.
The actual electronics are dead cheap. The last display I built cost £10 for the LCD, 50p for the pot, 5p for a resistor, £1.50 for a mono lead and 25p for a battery connector. You can wire it all up in 1/2 an hour. Like I said, the big problem is finding a housing.
If you want to try the Munro/PPO2 meter then
www.golemgear.com had some housings for sale a few months ago.
BTW if you ever fancy meeting up for some more test diving then I take my monsters to Dorothea where no-one can shout at me! I should have my new baby at the start of October.
Cheers,
Stuart