Brenyo, I'm sure this is a long-shot, but I'm having a bit of trouble getting in contact with Phatpiggie (I'm sure he's busy, not complaining here).
Looking at the cap for the Tempest, I'm wondering if there is a chance it would be able to be used with the Thermal Accumulator stem and bowl. Looks like the threading may be similar. Already have a Tempest on the way, but I managed to lose the cap of my TA while loading on a hike. Slipped off a magnet and down a cliff. I was a bit devastated. It's been the Anvil ever since.
I see you will be selling caps individually and I would love to revive this beautiful original run TA, along side my new Tempest. Thanks in advance!