I'm sure you could find some on Monero marketplaces listed on https://monerica.com/ like XMRBazaar, however generally like any tech I would recommend buying from reputable sources if possible, and installing the os yourself, however if need be I am sure some are sold pre-installed.

You can order one through SimplifiedPrivacy. They can preinstall it for you. You also have options to buy with Bitcoin or probably Lightning.

Do it yourself! It is dead simple with the web installer.