You basically have 4 widths to choose from for 27inch tires from a 25c narrow width to 37c fat width -see options below
|27 inch size||ISO||700c equivalent|
|27 x 1||630x25||25c|
|27 x 1 1/8||630x28||28c|
|27 x 1 1/4||630x32||32c|
|27 x 1 3/8||630x37||37c|
There are a bunch of companies making 27 inch tires including; Avenir, Bell, Cheng Shin, Continential, Kenda, Michelin, Panaracer, Schwable, and Vittoria to name the big ones. Just do a search on Amazon and you will see for yourself.
You can spend $8 a tire for some Cheng Shin gumwalls or $36 a tire for Continental gatorskins and every where in between.
You want a traditional gumwall, my favorite, you have choices in every size. I personally like the Kenda K35 which is a great looking tire, sturdy and a very good bang for the buck.
You like color matching the side walls or treads to your bike? your covered- check the selection from Junky Rusty Bikes
So if you want; skinny or fat, colored or black, hip or retro, road or cross, you have choices with 27 inch tires. Don't get me wrong 700c is a great size with tons of options just don't convert your old school 10 speed to a modern wheel size out of the misguided notion that there aren't many options for the old school 27 inch tires. That's just a myth.. As Always....