At first I thought there was no way here. But I reread and noticed
An important person at church is a teacher at a local high school and teaches culinary arts, and asked to borrow the waffle makers.
If this person professes to be a Christian (and you do as well), there is a straightforward solution, but that doesn't mean she will receive it well.
Matthew 18: 15 states
“If a fellow believer hurts you, go and tell him — work it out between the two of you. If he listens, you’ve made a friend." (It goes on to say, "If he won’t listen, take one or two others along so that the presence of witnesses will keep things honest, and try again. If he still won’t listen, tell the church. If he won’t listen to the church, you’ll have to start over from scratch, confront him with the need for repentance, and offer again God’s forgiving love.") (The Message)
Clearly you need not go as far, but there is good reason to confront this person: they have caused you harm (grief, anger, and resentment). They, as a Christian, should understand if you approach them in the spirit of Matt 18, to make reparations to your relationship. They have damaged that.
How to ask for redress...in way that does not destroy the relationship yet also assuages my disappointment and anger?
You can't do anything but ask. If this person cannot apologize in a meaningful way that repairs the relationship, you can accept that they are lacking in empathy and/or interpersonal skills, and you can either forgive, knowing you've done your part, or you can proceed, and talk to your pastor.
Good luck getting back antique waffle irons (honestly.) It would be great if you did, but for the sake of restitution, I would ask for new waffle irons myself. Then, even though it's not the same thing, you can continue the tradition while you're looking for the real thing.
Edited to add: For those who aren't Christians and who feel this is useless to them, I'd ask, what other options do you have? You have to either confront the person or forgive them.
Someone has hurt you. You have festering anger and disappointment because you were not treated like your hurt mattered.
If the harm done is grievous enough that forgiving them just isn't happening, and you want to approach the person (as the OP states in the question) in a way that won't ruin the relationship, this advice still holds.
Approach the person in the spirit of saving the relationship.
It takes courage, but it sends this message (even if it's not your primary motivation; even if your primary motivation is to deliver yourself of your hurt): our relationship is important to me. I don't think you realize it, but you damaged our relationship with your actions. I need to talk to you about it.
The principle is the same. Ask for a time to meet this person. Tell them why you want to meet. Let them pick the time and place so they feel some control. Then meet. Practice what you're going to say ahead of time. Be kind, even if they weren't. But be direct as well. Tell them how much lingering hurt you've experienced from their action, and how they dismissed it/reacted to it. Then wait for them to either recognize they need to do more, or to be defensive.
If they recognize the need to do more, great! You're on your way to reparation and redress.
If they are defensive (the will counter with "facts", not feelings), return the conversation to feelings; people can argue "facts", but they can't deny your feelings. If you concentrate on your feelings ("but I do feel hurt, even if you think I shouldn't"), they will either eventually relent and ask what they can do, or they will show that they place their own feelings and beliefs above your own, i.e. they are unable to empathize enough to repair the relationship.
At that point, you - if the relationship is more important - either ask for mediation, or you forgive. You did what you could, there is nothing more to do. But the person heard you.
Often, that's really what it takes, to be heard as a person with real feelings. Ideally then you're treated like one, too. But you can lead a horse to water...