Currently the only short-term health insurance available in Pennsylvania are UnitedHealthcare’s Golden Rule short-term policies. Here is a link to their quoting page:
Here is an article about the possible availability of other options in the near future:
Availability of short-term health insurance in Pennsylvania | healthinsurance.org
Here is a chart with state restrictions on the maximum length of short-term policies and which companies (Aetna and Cigna, by way of Allstate) offer them: