I am a semi-vegetarian ... if I had my way, I would eat a bit of chicken or tuna maybe once a week or so ... and that's exactly what I did when I lived on my own. But a year ago I moved to Alberta and am being given room and board so I can attend University. Alberta is BEEF country. You can't go anywhere here without having someone serve you beef. And I am NOT a big fan of beef.
And meals here are very meat-centric ..... a big slab of beef
<<shudder>> ...... and almost as an after-thought, maybe a bit of potatoes or veggies or something. So, I'm dealing with the situation you mention in my everyday life right now!!
As for touring, when I went to Australia, the initial plan was to stick to a very tight budget which didn't allow for the purchase of meat. My cycling partner and I stuck to that budget, and a basically meat-free diet, for nearly three weeks. Three weeks of riding approx. 100 kms a day. Toward the end of three weeks we were cranky, irritable, lethargic, and both of us CRAVED protein.
Then, two nights in a row, we were given meat by fellow campers in the campgrounds at which we were staying (the Australians are REALLY friendly!!) ..... and after that we made sure we had meat every day.
While we were in the southern part of Australia, and Tasmania, where it was cooler, we usually stopped at a store near the end of our day's journey and picked up a package of frozen, pre-made, hamburger patties, which we cooked up on the large BBQs which all Australian campgrounds have. Those packages usually contained 8 patties, and we ate them all! So there was no chance of them spoiling.
When we went to Queensland, our cycling plans changed because of the heat. We would ride early in the morning, then stop somewhere in the middle of the day, then ride again in the evening. Because we were rolling into our campsites so late, and because we were often bush camping during that time, so the BBQs weren't available, we changed our eating plans .... instead we started eating our big meal in the middle of the day while we were waiting out the heat. And our meals usually consisted of Australian hamburgers!!
Have you ever had an Australian hamburger??? You haven't had a hamburger until you've had an Australian hamburger!! Those things were entire meals all in one!! Bun, several hamburger patties, a fried egg or two, cheese, lettuce, tomatoes, onions, beets, pineapples, and the top bun!! And they were usually served with a newspaper full of fries!!! Mmmmmmm!!! All for about $5.00. That was basically what I ate ... small bowl of oatmeal in the morning, the Australian hamburger meal around noon, and a couple granola bars later in the day.
If you do want to stick to a vegetarian diet on a tour, keep in mind that you'll likely need more protein to keep up your cycling energy, rebuild your muscles etc. So, you might want to choose vegetarian foods which are high in protein. Soy products are supposed to be pretty good.