Complex sentence: These toys are currently sold only in the USA and Canada and availability online and in Hallmark stores has been unpredictable with long periods of time passing between the arrival of different production batches as Hallmark badly underestimated how popular these items would be.
Split into simpler sentences: These toys are currently sold only in the USA and Canada. Availability online and in Hallmark stores has been at best sporadic with long periods of time passing between the arrival of different production batches as Hallmark had badly underestimated how popular these items would be.