It's unavoidable. Arrangements have a finite lifespan. As others here have said, I've felt the pain you feel now. Sometimes she ended it either well with some type of closure, or not so well by simply ghosting. And sometimes I've had to end it, usually when the arrangement is no longer delivering the benefits we originally negotiated. They all hurt when they end.
There's an old joke that sort of applies here:
"Pizza! When it's good it's really great. And when it's bad it's still pretty good."
Here's my approach when I've seen a valued arrangement end:
1. Take a break. Don't be in any kind of hurry to find a replacement, because you won't. Each SB is unique, just as each woman is unique. When the NEXT SB opportunity arises, you'll know what to do. In the interim, if you have to get laid - because of course you do, we all do - use TER or whatever P4P resource you like.
2. Try to internally frame the past experience by appreciating all the good parts of the arrangement, rather than the pain of the breakup. This is a poor analogy, but I'll use it anyway: When was the last time you got $75 rib eye at Mortons or any top-shelf steak house? Your memory of that steak is all about how good it tasted, rather than how empty your plate looked when you finished eating.
So take some time to reflect on what you most appreciated about your SB and then use that to help define what you want to look for in your next.
And I too offer my ear for bending by PM as well. This is a journey we can share, for better or worse.
Life is good
The Cat