The Syndicomm online store is defunct now, it was most recently owned & run by the late Tony Diaz who died suddenly in late 2021. www.a2central.com has also vanished for the same reason, Tony was hosting that URL too. When I tried the store.syndicomm.com
URL just now, I got a ERR_CONNECTION_TIMED_OUT in my Chrome browser. https://www.callapple.org/call-apple/members-information/obituaries/apple-ii-hobbyist-tony-diaz-passes-away/