Oh, I’m sorry…I didn’t understand. You can sign up on the same list…just include a comment somewhere about you needing to purchase it because you don’t have a filter currently on order. They will send you a PayPal invoice for it when they get ready to ship it. (That’s how I got one…I signed up to test them, but didn’t have a filter on order at the time. So I bought one for the testing.) 
(And Dan hasn’t said otherwise, so it can’t hurt. ) 
If you want to wait though, they might set up something to offer them one day in the store after the Glowforge filters ship…Dan did say something about offering these as an alternative to the GF filter.