Are clear hydraulic brake lines available for sale?

Since all brake lines are not see through, the only way to determine if your brake needs a bleed is by feeling the brakes. If they are "squishy", then you need a brake bleed.

I’m of the opinion that sight would be more effective to determine if there are air bubbles in your system.

Are there clear hyrdraulic brake lines available for sale?

If they are not available, is there a techincal reason why they are not feasible?

Here’s some examples:

Seth Bikes Hacks How to Bleed MTB Brakes

Clear Shimano Hydrualic Brake