Better to add odd-duck page to current site, or create new site for it and send the link juice to the new site?

I have a site about new-age mediation kind of stuff, with a domain-authority ranking of about 40.

I have some ideas for a new and basically unrelated page about tattoo-related products.

Would it be better to

a) add that new, relatively unrelated page to my existing DA-40 site, and create some internal links from that site's highest-ranked pages to the new tattoo page, o

b) create a new domain (like TatooIdeaThing.net) and have some of the higher-ranking pages from the DA-40 site externally link to the new tattoo page ?

Which option do you think would get the new tattoo page more SEO traffic?