Single Pane Bay Windows

I have two single pane bay windows: one in the living room measuring 5' x 4' and one "triangular" window in our cathedral master bedroom high on the wall measuring 10' wide x 4' high. I have used those clear window films with a blow dryer to add some protection and it has helped. However, I still feel cold air leaking through. What else can I do to block outside cold air from getting through? The triangular window in the master is worse since we sleep there and it is difficult to keep our room warm during the winter.

You can get some low-e film and add that to the windows, but replacement is the best solution. The films are available in both clear and tinted or mirrored if you want to block more light and they also block most UV rays, so they help fading of interior fabrics and paint.

One thing I like better than the sealing film you are using is (custom) panels. They're made of a flexible, crystal clear plastic maybe 3/16" thick with a magnetic seal all around. The strip is left on the wall or frame, depending on where applied, and you may need to add a strip to get a good seal across the bottom, but you can get it so it is unobtrusive. They're easy to remove, but make a great seal. A second benefit is that they really block a lot of sound. This was quite awhile ago, but I was at a friends, staying for a few days. They were mowing the lawn right outside and it was hard to hear the mower. I lifted a corner and even with the window closed, it was like I was standing next to the thing.

I had a smaller window & went to a glass place
They cut me a thick piece of glass & I installed it
This was actually over a 2x pane window to cut down on noise from a busy street. Worked great

Are your referring to window tint similar to cars but for home windows? What brand do you recommend? Does this provide insulation? Would I have to take my shrink film off?

Where can I get these custom panels?

I'll call a local glass place but since my windows are a larger size it may be expensive.

leave your plastic up and look into some heavy curtains, some have liners that are heavy making them a good insulator.

I have a window that was installed poorly and leaks when it is windy, in the coldest months I use plastic then cover it with a thick blanket and that room stays much warmer.

The film I'm talking about is applied directly to the glass and is generally permanent (although it can be removed - not easy though). The film may be the same as that used on cars. I bought some in El Paso, TX - it was packaged with enough to do a glass sliding door. You can probably buy it in bulk. Look for a good low-e rating. The low-e function reflects IR energy, so you don't get as much conduction to the outside and the reflected room heat gets bounced back into the room. In the summer, it blocks the heat from outside. A side effect is they typically block UV rays as well. It's similar to what's installed in a good thermopane window, but they apply the coating to a sheet of plastic rather than the glass directly.

Haven't looked for those plastic panels...no idea where you can get them, but should show up in a careful google search.

No idea on the plastic panels.