Actually, Matt Struble sells them -- go figure!!!
Matt has contact information on the IDNIYRA website under the Suppliers/Hardware section. I'm not sure if the info is still up to date, but here is what's listed:
Strublized Chocks
Contact: Matt Struble
Wixom, Michigan
Phone: 248-669-4583
If this contact info doesn't work, please let me know and I can contact Matt and ask for updated info.
Paul - emial:
webmaster@idniyra.org