I can give you 420 GP for the helmet, and 240 GP for the gauntlet, bringing your credit up to 660 GP.

I've got two options for you on the goggles; 450 GP and 600 GP. For 450 you get a pair of tinted goggles which takes half a second to calibrate for the amount of light coming through them. In other words, you can use them to look into the sun but they won't protect you form a flashbang. For 600, the calibration happens instantaneously, meaning the goggles will include visual flashbang protection.

The enchanted katana would cost 3375 in prevalida, and for an enchantment like that I think top tier materials should be required, so I won't bother with the mythril price.

Let me know how you'd like to proceed.