High Pressure Transparent Tubing

How about gauge glass tubing, as used for checking water levels in boilers? A steam valve and accessories supplier would be a good source.

Great suggestion. I ran across this after making this post. It appears to do everything I need it to do. But I have yet to find a supplier of adapter fittings or compression fittings to attach anything to this tubing.

The suppliers who sell the tubing do not carry fittings, and the suppliers who carry fittings do not know anything about pyrex or glass boiler tubing.

Any suggestions?

How about just getting some 'replacement' glass cocks:

http://www.nciweb.net/tubular.htm

You can probably get the glass through them as well.

The usual device for this is a "gauge glass valve." They are made in various materials and configurations, and incorporate packing glands (like a compression fitting) with suitable seals depending on the type of fluid and temperature. McMaster-Carr might be a source. I used to use Seattle Steam Supply when I lived there; many cities would have a similar entity.

Looks like it's going to be pretty hard to find. What are you going to use it for?

That, I cannot tell you atm. I can just say it is something you would want to see.

drugs, alcohol or a big high pressure tea pipe

I've used clear PVC tubing. OK, pipe.

Pipe-Schedule 80

PVC clear sch 80 pipe has a degrade factor when temperatures increase above 73° F. At my required temperature range it specs to hold only about 100 PSI. Good suggestion tho.

You may want to check with a company called Bond Fluid Air, google that and if nothing else they will know who to send ya to.