This is from the old harmony video TK-8, starring Ashley Renee and Darla Crane. Very good video!
It's available at www.tickletickletickle.com (Harmony's subsidiary 'Consensual Touch') in the section 'Classic Tickling Videos'. Careful, TK-8, not TKL-8 ! But I've heard they might withdraw the older videos soon, so you'd better be quick.