I'm sorry that you are dealing with these new symptoms.
I use a Peltor X5A for chores like vacuuming, feeding my dog (she gets way too loud when she is hungry), turmix, blow drying my hair, etc. I have an Optime II as well, and I like it more, because it's much more comfortable, but the X5A is better.
I don't know how big your garden is and how smooth the lie of the land is, but last summer I bought a very basic push reel lawn mower. It's much quieter than the gas powered ones, but the sound of the blades are not nice, so I have earmuffs on as well. If your garden is smooth, not very steep and lumpy, I think it does a decent job.