Webcomic books can be oddly hard to track down. The same series might have a print run, a Kickstarter edition, a creator store copy, a publisher hardcover, and a dead shop link from ten years ago.
Start with official sources. For Nuklear Power comics, that means current Nuklear Power posts, Atomic Robo updates, and campaign pages mentioned by the creators. That path is slower than a marketplace search, but it keeps you closer to real stock, real edition details, and creator-supported sales.
Use resale marketplaces after that, especially for out-of-print indie comic books. Check condition photos, ISBNs when available, creator signatures, and whether the listing is a book, a PDF, a script collection, or a campaign add-on.