Just saw this. There are usually a lot of small, untowered airports around any Class D (C, B) airport. Many offer instruction. It would be unusual if an instructor with his own plane didn’t run an independent operation in your area. We don’t know where you are, so we can’t help in the search, but pull up the sectional for your area & start checking the smaller places. The interwebs should help. If the drive is a little long, consider two lessons a day with a couple of hours in between lessons. A nap & a coke does wonders between lessons.
If there are other instructors at the school where you are, chat them up or just listen to how they deal with their students. Yes, it is uncomfortable to fire an instructor but also stay at the same school. However, it’s done all the time & it sounds like your guy is on the verge of leaving anyway. You can always plead schedule conflicts or aircraft availability as the reason. Or, “I just wanted to get another instructor’s POV on my progress.” The breakup doesn’t have to be messy.
Also remember, if your instructor is in line to be picked up by the bigs, he will have no compunction about ditching you. In the end, it’s your money. You deserve good value.