I believe that The Hemp Center sells Discovery scopes still... might check there.

Otherwise, I'd recommend J&R Electronics, as that's the cheapest I've seen online... they're only like $58 and you can use them for everything from this purpose to checking harvest timing and looking for pests on your live plants. Great picture quality on the Discovery series (you can use it for website pictures and whatnot if you're an MMC), we got some AMAZING shots of some never-before-seen stuff with our scope that we'll be sharing with the community very soon.