Can's swear as to the May bloom, but here is one sold by Bluestone:

GERANIUM Nimbus-Cranesbill - Medium 20" - Plant 16" apart. zone 4-8. Arguably as good, or better than G. Johnson's Blue. Very floriferous and vigorous. Blue flowers with a pale center over attractive mounds of dissected leaves.

It blooms Late Spring, Early summer -> Summer, which is the same description they have for Mac.Bevan's Variety , which is just now coming into bloom in my yard. And I live near you.

Or you might try GERANIUM Wargrave Pink Medium - Plant 18" apart Shorter than Claridge Druce, 20" with salmon pink flowers. An old garden friend.

Thanks! Off to the nursery tomorrow! : )