Does Medigap coverage have an open enrollment period other than the initial 6 month period after a person turns 65?

Hi,

Does Medigap coverage have an open enrollment period other than the initial 6 month period after a person turns 65? Or can you sign up for Medigap coverage anytime after signing up for Medicare? I can only find open enrollment dates for Medicare (October 15 to December 7). I know if you sign up after the initial 6 month enrollment period you might pay more in premiums.

Thanks