Can we get a "delivered burn-down" report?

We'd love to show burn-up report that counts items that are marked as "delivered" rather than only those that are "accepted". Since our customers only accept items every few days rather than immediately upon delivery, we get into this situation where we can't see our iteration velocity until our customers accept our items. Obviously, we still need the burn-down/burn-up charts that measure only accepted items - but this report (possibly called "delivered burn-down" as opposed to "accepted burn-down") would be super-useful