Regarding suppliers in general, we stick with the ones that do good work for us, and we look for new ones in areas where we are not satisfied. I think the only real way to evaluate a supplier is to run a batch of parts through them and see the output and of course see how they respond to feedback and iterate.
I know you told us there are no plans for making new devices in near future, but one of my suggestions would be to consider making Passport waterproof or water resistant device.
This probably needs a lot of work in redesign of inside, but even cheaper solutions like waterproof cases for protection would be interesting, and you could sell them separately.
I already know several hardware wallets that started making waterproof devices, so better think about that on time.