Where could I find a transparent frying pan?

Corning made a Visions pan - I had a set and used it for years. You might find them on eBay or at a garage sale. I didn't really like it as a pan - took a long time to heat up and then stayed hot, thus making a gas stove into an electric and making an electric even less responsive. It's not completely clear, it's kind of brownish.

Just search on www.ebay.com for "Pyrex Flameware" and you will find things like :
Vintage Pyrex Flameware Saucepan Skillet + Handle SET
Vintage Pyrex Glass Flameware Skillet w/ Handles
1930's Pyrex Flameware saute pan w/ detachable handle
It is highly unlikely that you will find a new one. The reason is that the formula r for Pyrex before 1940 was way more resistant to thermal shock , but also more expensive. The current formula is more resistant to mechanical shocks but can not take rapid cooling (like adding cold liquid in a hot pan when you are making a ragu) without shattering.
I have no info on the advantages of a glass pan except the "cool factor"
Hope this info helps.