I am new to bikes and was wondering if there is a difference between inner tubes for a 27 x 1 1/4 bike and a 27 x 1 1/8 bike. My bike has 27 x 1 1/8 tires but I wanted to use 27 x 1 1/4 inner tubes since they are easier to find.
Should be fine in almost every case. The exception would be tubes that say "700x32-35 (27x1-1/4)", or anything else that has a 700C range where the starting number is larger than 28. That would be bigger than you want. (Would still probably work, but it wouldn't be ideal.) In other words, there isn't usually a difference, but only in the sense that most 27x1-1/4 tubes have that width on the top end of the range they cover rather than the bottom.
If you can't find one that just says 27x1-1/8, use anything that has 700x28 in its range. That's the answer you won't go wrong with. It's a tire for a different and more common rim size, but the tubes for it are interchangeable with 27x1-1/8. Make sure to get the right valve type.