I looked online, but could not find any source. There certainly must be one. I just picked up two (new) tanks and they were without caps. These tend to get detached and lost, so I would like to have a couple of spares. I don't feel comfortable having my spare tank in the locker without a cap and risk having the valve inadvertently turned on. I guess I could try to figure out who the distributor is and ask them, but I thought I would throw this out there in case anyone had successfully searched before.