NAWAS Travel is another one that provides trips to parishes. I have gone on 3 trips with them. They’re pretty good, although sometimes you are kind of rushed through the sites and on to the next thing, but that is true of all group tours. A parish where I attend Mass frequently is having a Holy Land trip next year. The priest gets to go for free and he also receives some kind of a fee from the travel agency for promoting the trip, that he then uses to fund the parish youth programs, so I am helping the church while having a vacation myself.
Edited to add, we always have Mass almost every day at some historic church, although sometimes we get a really awesome space in the church proper and other times we get what looks like a basement under repairs. The weirdest one was a cathedral in Budapest where the Mass was not even in the Cathedral but in some church space they had rented and set up with an altar, seats etc. under a pizza parlor across the street.