the law doesn't change the rules about people under the age of 65 covered by medicare being able to buy medigap plans. plans aren't required by federal law to sell these plans to people under the age of 65 though some states allow it. it sounds like you've already checked and live in a state that does not require it but you can inquire further at medicare. gov.
does the aca now allow supplemental insurance policies to be purchased by people covered by medicare disability?