Like a whole separate Discourse instance linked to the same Stripe account? Yes, that will work.
Not entirely sure of your use case but you can add a separate product to your existing Discourse site that you can use for your fundraising events. If you don’t want to have it show up on on your subscriptions page you can hide it with css, but still link to it directly at /s/prod_id_asdf. Maybe we should add a “hidden” option so that products can be “active” but “hidden”.